April 1997 arXiv papers — page 7

Lars M. Johansen

A generalized form of EPR state is defined, embracing both classical and nonclassical states. It is shown that for such states, Bell's inequality is equivalent to a constraint on stochastic field theories. Thus, violation of Bell's inequality can be observed also for weak violation of stochastic field theories. The Schrodinger cat state is shown to b

David Craig

The geometry of decoherence in generalized "consistent histories" quantum theory is explored, revealing properties of the theory that are independent of any particular application of it. It is shown how the decoherence functional of a closed quantum system may be regarded as an Hermitian form on the space of linear operators on the Hilbert space of t

David Fairlie, Ming-Yuan Wu

After obtaining some useful identities, we prove an additional functional relation for $q$ exponentials with reversed order of multiplication, as well as the well known direct one in a completely rigorous manner.

S. Flach, C. R. Willis

Nonlinear classical Hamiltonian lattices exhibit generic solutions in the form of discrete breathers. These solutions are time-periodic and (typically exponentially) localized in space. The lattices exhibit discrete translational symmetry. Discrete breathers are not confined to certain lattice dimensions. Necessary ingredients for their occurence are the exi

M. A. Ivanov, Yu. L. Kalinovsky, P. Maris, C. D. Roberts

The semileptonic and leptonic decays of heavy mesons are studied as a phenomenological application and exploration of a heavy-quark limit of Dyson-Schwinger equations. The single form factor, $ξ(w)$, which characterises the semileptonic decay in this limit, is calculated and compares well with recent experimental extractions. We obtain a lower bound of 1/3 o

V. V. Sokolov, I. Rotter, D. V. Savin, M. Müller

The mixing of the doorway components of a giant resonance (GR) due to the interaction via common decay channels influences significantly the distribution of the multipole strength and the energy spectrum of the decay products of the GR. The concept of the partial widths of a GR becomes ambiguous when the mixing is strong. In this case, the partial widths det

G. Rasche, A. Gashi

The hadronic properties of the pionium ion (Coulomb bound system of three charged pions) are estimated using the results for the positronium ion $P{s}^{-}$. It turns out that the hadronic shift of the ground state energy and the lifetime of the pionium ion are approximately the same as for pionium.

V. V. Sokolov, I. Rotter, D. V. Savin, M. Müller

A phenomenological schematic model of multipole giant resonances (GR) is considered which treats the external interaction via common decay channels on the same footing as the coherent part of the internal residual interaction. The damping due to the coupling to the sea of complicated states is neglected. As a result, the formation of GR is governed by the in

Hungchong Kim, Su Houng Lee

We calculate the coupling constants, $g_{πNS_{11}}$ and $g_{ηNS_{11}}, using QCD sum rules in the presence of an external meson field. A covariant derivative is introduced within the S_{11} interpolating field so that in the nonrelativistic limit the field dominantly reduces to two quarks in the s-wave state and one quark in the p-wave state. Our result for

Cameron McA. Gordon

This is an expository paper, in which we give a summary of some of the joint work of John Luecke and the author on Dehn surgery. We consider the situation where we have two Dehn fillings $M(α)$ and $M(β)$ on a given 3-manifold $M$, each containing a surface that is either essential or a Heegaard surface. We show how a combinatorial analysis of the graphs of

Cameron McA. Gordon, Ying-Qing Wu, Xingru Zhang

We show that on any hyperbolic knot in $S^3$ there is at most one non-integral Dehn surgery which yields a manifold containing an incompressible torus.

Ying-Qing Wu

This article is solicited by C.\ Adams for a special issue of {\it Chaos, Solitons and Fractals\/} devoted to knot theory and its applications. We present some recent results about Dehn surgeries on arborescent knots and links.

Sergey Ivashkovich

We prove an analogue of E. Levi's Continuity Principle for meromorphic mappings with values in arbitrary compact complex manifolds in place of the Riemann sphere $\cc\pp^1$. The result is achieved by introducing a new extension method for meromorphic mappings. One of the corollaries reads as follows: If a compact complex surface $X$ is not "among the known o

Olivier Lessmann

The study of classes of models of a finite diagram was initiated by S. Shelah in 1969. A diagram D is a set of types over the empty set, and the class of models of the diagram D consists of the models of T which omit all the types not in D. In this work, we introduce a natural dependence relation on the subsets of the models for the omega-stable case which s

G. Baumsalg, M. Shapiro, H. Short

We define a class of groups based on parallel computations by pushdown automata. This class generalizes automatic groups. It includes the fundamental groups of all 3-manifolds which obey Thurston' s geometrization conjecture. It also includes nilpotent groups of arbitrary class and polynomial degree isoperimetric inequality. It is closed under wreath pro

H. W. L. Naus, H. J. Pirner, T. J. Fields, J. P. Vary

Starting from the QCD Lagrangian, we present the QCD Hamiltonian for near light cone coordinates. We study the dynamics of the gluonic zero modes of this Hamiltonian. The strong coupling solutions serve as a basis for the complete problem. We discuss the importance of zero modes for the confinement mechanism.

E. Ivanov

I give an overview of recent progress in constructing the KdV, mKdV and NLS type hierarchies with extended N=4 supersymmetry.

Igor Tyutin, Mikhail Vasiliev

Lagrangian formulation of free massive fields corresponding to irreducible representations of the Poincare group of arbitrary integer and half-integer spins in three-dimensional space-time is presented. A relationship of the theory under consideration with the self-duality equations in four dimensions is discussed.

K. Bautier, S. Deser, M. Henneaux, D. Seminara

We show, in two complementary ways, that D=11 supergravity---in contrast to all its lower dimensional versions---forbids a cosmological extension. First, we linearize the putative model about an Anti de Sitter background and show that it cannot even support a "global" supersymmetry invariance; hence there is no Noether construction that can lead to a

L. Bonora, A. Sorin

The first two Hamiltonian structures and the recursion operator connecting all evolution systems and Hamiltonian structures of the N=2 supersymmetric (n,m)-GNLS hierarchy are constructed in terms of N=2 superfields in two different superfield bases with local evolution equations. Their bosonic limits are studied in detail. New local and nonlocal bosonic and

M. Carena, C. E. M. Wagner

Electroweak Baryogenesis is a particularly attractive theoretical scenario, since it relies on physics which can be tested at present high energy collider facilities. Within the Standard Model, it has been shown that the requirement of preserving the baryon number generated at the weak scale leads to strong bounds on the Higgs mass, which are already inconsi

Dirk-U. Jungnickel, C. Wetterich

We compare the linear meson model and chiral perturbation theory in next to leading order in the quark mass expansion. In particular, we compute the couplings L_4--L_8 of chiral perturbation theory as functions of the parameters of the linear model. They are induced by the exchange of 0^{++} scalar mesons. We use a phenomenological analysis of the effective

R. Peschanski

Using the QCD dipole picture of BFKL dynamics and the conformal invariance properties of the BFKL kernel in transverse coordinate space, we show that the 1--to--p dipole densities can be expressed in terms of dual Shapiro- Virasoro amplitudes B{2p+2} and their generalization including non-zero conformal spins. We discuss the possibility of an effective close

Keiichi Akama

The Nambu-Jona-Lasinio model is the special case of the renormalized Yukawa model with the compositeness condition. We use it to calculate the effective coupling constants in terms of the compositeness sale (momentum cut off) at the next-to-leading order in 1/N. The next-to-leading correction is too large in the model of scalar composite, while that in the i

Hiroaki Kodama, Yoshimi Matsubara, Shigeyoshi Ohno, Tsuneo Suzuki

We calculate inter-meson potentials numerically by solving classical equations of motion derived from Dual Ginzburg-Landau (DGL) Theory. Inter-meson potentials in DGL theory are shown to be similar to those of the string-flip model and well reproduce behaviors of the short-range interaction at the classical level. We also compare our results with those from

ZEUS Collaboration, M. Derrick et al

Diffractive dissociation of quasi-real photons at a photon-proton centre of mass energy of W ~ 200 GeV is studied with the ZEUS detector at HERA. The process under consideration is gamma p -> X N, where X is the diffractively dissociated photon system of mass M_X and N is either a proton or a nucleonic system with mass M_N < 2GeV. The cross section for this

L. H. Ford, N. F. Svaiter

The quantum fluctuations of horizons in Robertson-Walker universes and in the Schwarzschild spacetime are discussed. The source of the metric fluctuations is taken to be quantum linear perturbations of the gravitational field. Lightcone fluctuations arise when the retarded Green&#39;s function for a massless field is averaged over these metric fluctuations.

William M. Pezzaglia, John J. Adams

Standard formulation is unable to distinguish between the (+++-) and (---+) spacetime metric signatures. However, the Clifford algebras associated with each are inequivalent, R(4) in the first case (real 4 by 4 matrices), H(2) in the latter (quaternionic 2 by 2). Multivector reformulations of Dirac theory by various authors look quite inequivalent pending th

Ferenc Pazmandi, Richard T. Scalettar, Gergely T. Zimanyi

For phase transitions in disordered systems, an exact theorem provides a bound on the finite size correlation length exponent: ν_{FS}<= 2/d. It is believed that the true critical exponent νof a disorder induced phase transition satisfies the same bound. We argue that in disordered systems the standard averaging introduces a noise, and a corresponding new div

J. C. A. Barata, D. H. U. Marchetti

Some results on the two-point function and on the analytic structure of the momenta of the effective fugacity at the origin for a class of diluted ferromagnetic Ising models on the Cayley tree are presented.

H. Rieger, F. Igloi

Dynamical correlations of the spin and the energy density are investigated in the critical region of the random transverse-field Ising chain by numerically exact calculations in large finite systems (L<=128). The spin-spin autocorrelation function is found to decay proportional to (log t)^{-2x_m} and (log t)^{-2x_m^s} in the bulk and on the surface, respecti

I. V. Krive, P. Sandström

The persistent current for a one-dimensional ring with two tunnel barriers is considered in the limit of weakly interacting electrons. In addition to a small off-resonance current, there are two kinds of resonant behavior; (i) a current independent of the barrier transparency (true resonance) and (ii) a current analogous to the one for a ring with only a sin

E. Kanzieper, V. Freilikher

Joint distribution function of N eigenvalues of U(N) invariant random-matrix ensemble can be interpreted as a probability density to find N fictitious non-interacting fermions to be confined in a one-dimensional space. Within this picture a general formalism is developed to study the eigenvalue correlations in non-Gaussian ensembles of large random matrices

H. Arisue, K. Tabata

The low-temperature series are calculated for the free energy, magnetization and susceptibility in the Q-state Potts model on the square lattice, using the improved algorithm of the finite lattice method. The series are obtained to the order of $z^{41}$ for each of Q=5-50, and the result of their Padé type analysis is compared with those of the large-Q expan

Masanori Ichioka, Naoki Enomoto, Kazushige Machida

The vortex lattice structure in a d_{x^2-y^2}-wave superconductor is investigated near the upper critical magnetic field in the framework of the Ginzburg Landau theory extended by including the correction terms such as the higher order derivatives derived from the Gor&#39;kov equation. On lowering temperature, the unit cell shape of the vortex lattice gradua

Cristopher Moore, Mats G. Nordahl

We show that predicting the HPP or FHP III lattice gas for finite time is equivalent to calculating the output of an arbitrary Boolean circuit, and is therefore P-complete: that is, it is just as hard as any other problem solvable by a serial computer in polynomial time. It is widely believed in computer science that there are inherently sequential problems,

Jennifer Chu-Carroll, Michael K. Brown

In this paper, we argue for the need to distinguish between task and dialogue initiatives, and present a model for tracking shifts in both types of initiatives in dialogue interactions. Our model predicts the initiative holders in the next dialogue turn based on the current initiative holders and the effect that observed cues have on changing them. Our evalu

Anthony Mezzacappa

In one dimension, we present results from comparisons of stationary state multigroup flux-limited diffusion and Boltzmann neutrino transport, focusing on quantities central to the postbounce shock reheating. In two dimensions, we present results from simulations that couple one-dimensional multigroup flux-limited diffusion to two-dimensional PPM hydrodynamic

D. A. Frail, S. R. Kulkarni, E. Costa, F. Frontera

We report on a comprehensive radio monitoring program of the bright gamma-ray burster GRB970111. These VLA observations were made at a frequency of 1.4 GHz and span a range of post-burst timescales between 28 hours and one month. Despite extensive sampling at sub-milliJansky sensitivities, no radio source was detected above 0.5 mJy in the current best error

D. Fargion, A. Salis

Time evolution and signature of GRB 970228 are analysed in the framework of fireball or precessing gamma jet models

Y. Dabrowski, A. C. Fabian, K. Iwasawa, A. N. Lasenby

Recent X-ray observations have shown broad, skewed iron line emission from Seyfert 1 galaxies which is explained by the emission being fluorescence on a disk close to a black hole. During one interval, the line in MCG--6-30-15 was so broad and redshifted that a Kerr black hole is implied. We are therefore studying the effects of the Kerr metric on the line p

D. J. Fixsen, G. Hinshaw, C. L. Bennett, J. C. Mather

We analyze the Cosmic Microwave Background (CMB) anisotropy data from the independent COBE FIRAS and DMR observations. We extract the frequency spectrum of the FIRAS signal that has the spatial distribution seen by DMR and show that it is consistent with CMB temperature fluctuations in the radiation well into the Wien region of the spectrum. Conversely, we f

Darja N. Drozdova, Ivan E. Panchenko

We examine and develop the model of gamma ray bursts origin proposed by Shaviv and Dar (astro-ph/9606032), according to which the strong gamma ray emission is produced by the interaction of the baryonic relativistic jet (outflow) with the soft photon field in a dense stellar region. It is shown by the simulations of the burst profiles that these profiles are

Martin Kerscher, Jens Schmalzing, Thomas Buchert, Herbert Wagner

In an analysis of the IRAS 1.2 Jy redshift catalogue, with emphasis on the separate examination of northern and southern parts (in galactic coordinates), we found that the clustering of galaxies differs significantly between north and south, showing fluctuations in the clustering properties at least on scales of 100 Mpc/h (Kerscher et al. 1997, astro-ph/9704

Garrelt Mellema

Using a radiation-hydrodynamics code I follow the formation of planetary nebulae around stars of different mass. Because a more massive central star evolves much faster than a lower mass one, it is to be expected that this will affect the formation of the PN. For the stars I use the evolutionary tracks for remnants with masses of 0.605 M0 and 0.836 M0, taken

Adam Frank, Garrelt Mellema

We present the results of numerical hydrodynamic models for the collimation of outflows from young stellar objects. We show that the presence of a toroidal environment can lead to efficient formation of jets and bipolar outflows from initially uncollimated central winds. The interaction between the wind and the environment leads to two types of collimation,

Rodney M. Smith, Simon P. Driver, Steven Phillipps

From deep CCD observations of the cluster Abell 2554 we have recovered the cluster&#39;s luminosity distribution over a wide range of magnitude (-24 < M(R) < -16). We compare the derived A2554 cluster luminosity function (at redshift 0.1) with that of the local Coma Cluster (A1656) and the more distant (z = 0.2) cluster A963. The distribution is remarkably s

Kailash C. Sahu

More than 100 microlensing events have been detected during the last ~4 years, most of them towards the Galactic Bulge. Since the line of sight towards the Bulge passes through the disk and the Bulge itself, the known stars towards the Bulge play a dominant role as gravitational lenses. If these stars have planets around them, then the signature of the plane

Steven L. Kleiman

After reviewing Bertini&#39;s life story, a fascinating drama, we make a critical examination of the old statements and proofs of Bertini&#39;s two fundamental theorems, the theorem on variable singular points and the theorem on reducible linear systems. We explain the content of the statements in a way that is accessible to a nonspecialist, and we develop v

Kan Chen

We propose a general learning algorithm for solving optimization problems, based on a simple strategy of trial and adaptation. The algorithm maintains a probability distribution of possible solutions (configurations), which is updated continuously in the learning process. As the probability distribution evolves, better and better solutions are shown to emerg

G. F. Giudice, R. Rattazzi

The reported anomaly in deep-inelastic scattering at HERA has revived interest in the phenomenology of R-parity violation. From the theoretical point of view, the existence of R-violating interactions poses two considerable problems. The first one concerns the flavour structure of the interactions and the origin of an appropriate suppression of flavour-chang

S. Kuhlmann, H. L. Lai, W. K. Tung

The recently reported excess of events at HERA compared to QCD calculations impels us to examine all possible Standard Model explanations before invoking ``new physics&#39;&#39;. We explore the possibility of adding an unusual, but small, component of additional quarks at large x (beyond x>0.75) as a way to increase the predicted SM cross-section in the HERA

Ue-Li Pen, Uros Seljak, Neil Turok

An efficient technique for computing perturbation power spectra in field ordering theories of cosmic structure formation is introduced, enabling computations to be carried out with unprecedented precision. Large scale simulations are used to measure unequal time correlators of the source stress energy, taking advantage of scaling during matter and radiation

Eugene Perevalov, Harald Skarke

We explain the observation by Candelas and Font that the Dynkin diagrams of nonabelian gauge groups occurring in type IIA and F-theory can be read off from the polyhedron $Δ^*$ that provides the toric description of the Calabi-Yau manifold used for compacification. We show how the intersection pattern of toric divisors corresponding to the degeneration of el

I. Chepelev, A. A. Tseytlin

We discuss long-distance, low-velocity interaction potentials for processes involving longitudinally boosted M5-brane (corresponding in type IIA theory language to the 1/4 supersymmetric bound state of 4-brane and 0-brane). We consider the following scattering configurations: (a) D=11 graviton off longitudinal M5-brane, or, equivalently, 0-branes off margina

S. F. King, G. K. Leontaris

Motivated by the recent HERA events which are consistent with a possible leptoquark interpretation, we discuss the prospects for including additional light colour triplets and anti-triplets in the spectrum of supersymmetric unified theories. We focus on a particular string-inspired Pati-Salam model, and propose a simple mechanism by which a light colour trip

Tae-Sun Park, Hong Jung, Dong-Pil Min

The axial-vector coupling constant in nuclear medium is systematically studied using chiral perturbation theory. For normal nuclear matter, the first non-trivial corrections are estimated based on the independent particle approximation taking into account nuclear correlations in nuclear medium. The one-pion-exchange (OPE) two-body interactions turn out to en

Jorge Kurchan, Luca Peliti, Mauro Sellitto

We investigate the aging behavior of lattice-gas models with constrained dynamics in which particle exchange with a reservoir is allowed. Such models provide a particularly simple interpretation of aging phenomena as a slow approach to criticality. They appear as the simplest three dimensional models exhibiting a glassy behavior similar to that of mean field

Tetsuo Deguchi, Ruihong Yue

The Bethe ansatz equations of the 1-D Hubbard model under open boundary conditions are systematically derived by diagonalizing the inhomogeneous transfer matrix of the XXX model with open boundaries. Through the finite-size correction, we obtain the energy spectrum of the open chain and discuss the effects of boundary magnetic fields applied only at the edge

G. Brunetti, G. Setti, A. Comastri

In the framework of the quasar-radio galaxies unification the radio emitting lobes of FRII radio galaxies are pervaded by an intense quasar radiation field.Inverse Compton (IC) scattering between the relativistic electrons and the IR-optical photons from a hidden quasar may provide an important contribution to the X-ray emission of these radio galaxies. The

Koji Hashimoto, Hiroyuki Hata

We construct a system of bosonic closed string field theory coupled to a D-brane. The interaction between the D-brane and closed string field is introduced using the boundary state which is a function of constant field strength $F_{μν}$ and the tilt $θ_μ^i$ of the D-brane. We find that the gauge invariance requirement on the system determines the $(F_{μν},θ_

O. Megged

We propose a model in which a spliced vector bundle (with an arbitrary number of gauge structures in the splice) possesses a geometry which do not split. The model employs connection 1-forms with values in a space-product of Lie algebras, and therefore interlaces the various gauge structures in a non-trivial manner. Special attention is given to the structur

Eric W. Deutsch, Scott F. Anderson, Bruce Margon, Ronald A. Downes

We report results from Hubble Space Telescope WFPC2 imaging of the field of the luminous, bursting X-ray source in the globular cluster NGC 6441. Although the X-ray position is known to a precision of a few arcseconds, this source is only ~6&#39;&#39; from the cluster center, and the field contains hundreds of stars within the 3&#39;&#39; X-ray error circle,

Ken Umeno

We show non-integrability of the nonlinear lattice of Fermi-Pasta-Ulam type via the singularity analysis(Picard-Vessiot theory) of normal variational equations of Lamé type.

Holger F. Hofmann, Guenter Mahler

We present an exactly solvable model for photon emission, which allows us to examine the evolution of the photon wavefunction in space and time. We apply this model to coherent phenomena in three-level systems with a special emphasis on the photon detection process.

L. Accardi, I. V. Volovich

A model of a system driven by quantum white noise with singular quadratic self--interaction is considered and an exact solution for the evolution operator is found. It is shown that the renormalized square of the squeezed classical white noise is equivalent to the quantum Poisson process. We describe how equations driven by nonlinear functionals of white noi

D. Yu. Akimov, A. A. Burenkov, V. F. Kuzichev, V. L. Morgunov

A scintillation proportional counter with wavelength shifting fiber readout filled with Xe or Kr under a pressure of up to 20 atm is proposed for the low-background experiments on search for dark matter of the Universe and 2K-decay of 78 Kr.

Gerhard Hummer, Lawrence R. Pratt, Angel E. Garcia, Bruce J. Berne

Theories of solvation free energies often involve electrostatic potentials at the position of a solute charge. Simulation calculations that apply cutoffs and periodic boundary conditions based on molecular centers result in center-dependent contributions to electrostatic energies due to a systematic sorting of charges in radial shells. This sorting of charge

Miklos Gyulassy, Larry McLerran

The classical Yang-Mills radiation computed in the McLerran-Venugopalan model is shown to be equivalent to the gluon bremsstrahlung distribution to lowest order in pQCD. The classical distribution is also shown to match smoothly onto the conventional pQCD mini-jet distribution at a scale characteristic of the initial parton transverse density of the system.

D. Dalmazi, A. de Souza Dutra

By studying classical realizations of the sl(2,R) algebra in a two dimensional phase space $(q,π)$, we have derived a continuous family of new actions for free anyons in 2+1 dimensions. For the case of light-like spin vector $(S_μS^μ=0)$, the action is remarkably simple. We show the appearence of the Zitterbewegung in the solutions of the equations of motion

J. C. Brunelli, A. Das

We construct a new supersymmetric two boson (sTB-B) hierarchy and study its properties. We derive the conserved quantities and the Hamiltonian structures (proving the Jacobi identity) for the system. We show how this system gives the sKdV-B equation and its Hamiltonian structures upon appropriate reduction. We also describe the zero curvature formulation of

Thomas G. Rizzo

The capability of current and future measurements at low and high energy $e^+e^-$ colliders to probe for the existence of anomalous, CP conserving, $τνW$ dipole moment-type couplings is examined. At present, constraints on the universality of the tau charged and neutral current interactions as well as the shape of the $τ\to \ell$ energy spectrum provide the

R. Jakob, P. J. Mulders, J. Rodrigues

The representation of quark distribution and fragmentation functions in terms of non-local operators is combined with a simple spectator model. This allows us to estimate these functions for the nucleon and the pion ensuring correct crossing and support properties. We give estimates for the unpolarized functions as well as for the polarized ones and for subl

Jarkko Ahonen, Kari Enqvist

We consider the formation of a ring-like magnetic field in collisions of bubbles of broken phase in an abelian Higgs model. Particular attention is paid on multiple collisions. The small collision velocity limit, appropriate to the electroweak phase transition, is discussed. We argue that after the completion of the electroweak phase transition, when average

D. V. Shirkov, I. L. Solovtsov

We discuss the new model expression $\barα_{an}(Q^2)$ recently obtained for the QCD running coupling with a regular ghost-free behavior in the &#34;low $Q^2$&#34; region. Being deduced from the standard &#34;asymptotic-freedom&#34; expression by imposing the $Q^2$-analyticity -- without any adjustable parameters -- it obeys nice features: (i) The universal l

A. Ali Khan, J. Shigemitsu, S. Collins, C. T. H. Davies

We present a quenched lattice calculation of heavy-light meson decay constants, using non-relativistic (NRQCD) heavy quarks in the mass region of the $b$ quark and heavier, and clover-improved light quarks. The NRQCD Hamiltonian and the heavy-light current include the corrections at first order in the expansion in the inverse heavy quark mass. We study the d

Claus Lämmerzahl

The coupling of space-time torsion to the Dirac equation leads to effects on the energy levels of atoms which can be tested by Hughes-Drever type experiments. Reanalysis of these experiments carried out for testing the anisotropy of mass and anomalous spin couplings can lead to the till now tightest constraint on the axial torsion by $K \leq 1.5 . 10^{-15} m

C. Untiedt, G. Rubio, S. Vieira, N. Agrait

The shape of metallic constrictions of nanoscopic dimensions (necks) formed using a scanning tunneling microscope (STM) is shown to depend on the fabrication procedure. Submitting the neck to repeated plastic deformation cycles makes possible to obtain long necks or nanowires. Point-contact spectroscopy results show that these long necks are quite crystallin

M. Marsili, Y. -C. Zhang

We investigate the fluctuations induced by irrationality in simple games with a large number of competing players. We show that Nash equilibria in such games are ``weakly&#39;&#39; stable: irrationality propagates and amplifies through players&#39; interactions so that huge fluctuations can results from a small amount of irrationality. In the presence of mul

C. M. Marques, T. Charitat, D. Izzo, E. Mendes

We calculate the scattering intensity of dilute and semi-dilute solutions of star polymers. The star conformation is described by a model introduced by Daoud and Cotton. In this model, a single star is regarded as a spherical region of a semi-dilute polymer solution with a local, position dependent screening length. For high enough concentrations, the outer

Margit Steiner, Wolfgang Häusler

The transport properties of a tunnel barrier in a one-dimensional wire are investigated at finite voltages and temperatures. We generalize the Luttinger model to account for finite ranges of the interaction. This leads to deviations from the power law behaviour first derived by Kane and Fisher. At high energies the influence of the interaction disappears and

Mauro Sellitto, Mario Nicodemi, Jeferson J. Arenzon

We study the equilibrium properties of the Blume-Emery-Griffiths model with bilinear quenched disorder in the case of attractive as well as repulsive biquadratic interactions. The global phase diagram of the system is calculated in the context of the replica symmetric mean field approximation.

Indrani Bose

The effect of rotational constraint on the properties of lattice models like the self-avoiding walk, lattice animals and percolation is discussed. The results obtained so far, using a variety of exact and approximate techniques, are described. Examples of the rotational constraint in real systems are also given.

Hari M. Koduvely, Deepak Dhar

We define a new model of interface roughening which has the property that the minimum of interface height is conserved locally during the growth. This model corresponds to the limit $q \to \infty$ of the q-color dimer deposition-evaporation model introduced by us earlier [Hari Menon M K and Dhar D 1995 J. Phys. A: Math. Gen. 28 6517]. We present numerical ev

Martin Z. Bazant, Efthimios Kaxiras, J. F. Justo

We use recent theoretical advances to develop a new functional form for interatomic forces in bulk silicon. The theoretical results underlying the model include a novel analysis of elastic properties for the diamond and graphitic structures and inversions of ab initio cohesive energy curves. The interaction model includes two-body and three-body terms which

Maxim Yu. Kagan, Raymond Frésard, Massimiliano Capezzali, Hans Beck

We calculate the one-electron spectral function of the attractive (negative-$U$) Hubbard model. We work in the intermediate coupling and low density regime and obtain the self-energy in an approximate analytical form. The excitation spectrum is found to consist of three branches. The results are obtained in a framework, based on the self-consistent T-matrix

Shou-Cheng Zhang

This paper gives a simple introduction to the SO(5) theory of high T_c superconductivity. Current status and relation to experiments are summarized.

Gary Steigman, Sueli M. Viegas, Ruth Gruenwald

There is evidence for temperature fluctuations in Planetary Nebulae and in Galactic HII regions. If such fluctuations occur in the low-metallicity, extragalactic HII regions used to probe the primordial helium abundance, the derived 4He mass fraction, Y_P, could be systematically different from the true primordial value. For cooler, mainly high-metallicity H

M. H. Salamon, F. W. Stecker

We calculate the absorption of 10-500 GeV gamma-rays at high redshifts. This calculation requires the determination of the high-redshift evolution of the intergalactic starlight photon field, including its IR-UV spectral energy distribution. To estimate this evolution, we have followed a recent analysis of Fall, Charlot and Pei which gives results consistent

Jens Schmalzing

We introduce Koenderink filters as novel tools for statistical cosmology. Amongst several promising applications, they provide a test for the Gaussianity of random fields. We focus on this application and present some preliminary results from an analysis of the Cosmic Microwave Background (CMB).

Chris J. Willott, Steve Rawlings, Katherine M. Blundell, Mark Lacy

We present details of a new sample of radio-loud quasars drawn from 0.013 sr of the 7C Redshift Survey. This sample is small (21 quasars) but complete in that every object with an unresolved nucleus and/or broad emission lines with S(151MHz) > 0.5 Jy has been discovered. The dependence of the quasar fraction with redshift and radio luminosity is investigated

K. S. Cheng, Z. G. Dai

We propose that when neutron stars in low-mass X-ray binaries accrete sufficient mass and become millisecond pulsars, the interiors of these stars may undergo phase transitions, which excite stellar radial oscillations. We show that the radial oscillations will be mainly damped by gravitational-wave radiation instead of internal viscosity. The gravitational

B. Allen, R. R. Caldwell, S. Dodelson, L. Knox

We have computed an estimate of the angular power spectrum of the Cosmic Microwave Background (CMB) induced by cosmic strings on angular scales $>~ 15&#39;$, using a numerical simulation of a cosmic string network; and decomposed this pattern into scalar, vector, and tensor parts. We find no evidence for strong acoustic oscillations in the scalar anisotropy

A. Aparicio, C. Gallart, G. Bertelli

The star formation history (SFH) of the Pegasus dIr, a likely Local Group member at 0.95 Mpc from the Milky Way, is investigated. We characterize the SFH by two basic functions: the star formation rate, psi(t), and the chemical enrichment law, Z(t). It has been derived by comparing the color-magnitude diagram of the resolved stars in Pegasus, with a total of

S. P. Driver, W. J. Couch, S. C. Odewahn, R. A. Windhorst

We demonstrate the ability to recover morphological luminosity distributions within medium redshift clusters (z ~ 0.55) based on Hubble Space Telescope WFPC2 observations. We postulate that a detailed survey of the morphological LDs in local, low and medium redshift clusters may provide strong constraints on the modes of galaxy evolution in rich clusters. Pr

Andreas A. Berlind, A. C. Quillen, R. W. Pogge, K. Sellgren

We measure the extinction law in a galaxy&#39;s spiral arm and interarm regions using a visual and infrared (BVRJHK) imaging study of the interacting galaxies NGC 2207 and IC 2163. This is an overlapping spiral galaxy pair in which NGC 2207 partially occults IC 2163. This geometry enables us to directly measure the extinction of light from the background gal

Theo de Jong

In this article we give an algorithm for computing the integral closure of a reduced Noetherian ring R, in case this integral closure is finitely generated over R.

Igor F. Herbut

We study the continuum version of the dual theory for a system of two-dimensional, zero temperature, disordered bosons, interacting with short range repulsion and at a commensurate density. The dual theory, which describes vortices in the bosonic ground state, and has a form of 3D classical scalar electrodynamics in random, correlated magnetic field, admits

F. Abe

We present evidence for dilepton events from t tbar production with one electron or muon and one hadronically decaying tau lepton from the decay t tbar -> (l nu_l) (tau nu_tau) b bbar, (l=e, mu), using the Collider Detector at Fermilab (CDF). In a 109 pb^-1 data sample of p pbar collisions at sqrt(s) = 1.8 TeV we expect ~1 signal event and a total background

Ralph A. M. J. Wijers, Martin J. Rees, Peter Meszaros

The location accuracy of the BeppoSAX Wide Field Cameras and acute ground-based followup have led to the detection of a decaying afterglow in X rays and optical light following the classical gamma-ray burst GRB 970228. The afterglow in X rays and optical light fades as a power law at all wavelengths. This behaviour was predicted for a relativistic blast wave