August 1998 arXiv papers — page 13

Stephen C. Creagh, Niall D. Whelan

It is shown that tunnelling splittings in ergodic double wells and resonant widths in ergodic metastable wells can be approximated as easily-calculated matrix elements involving the wavefunction in the neighbourhood of a certain real orbit. This orbit is a continuation of the complex orbit which crosses the barrier with minimum imaginary action. The matrix e

E. M. Shahverdiev

For the first time an example of marginal hyperchaos synchronization with a single driving variable within the replica approach is presented. It has been demonstrated that in some cases one can perform hyperchaos synchronization only using the fact of positiveness of even part of nonlinear system's parameter.

Eric Sandquist, Ronald E. Taam, D. N. C. Lin, Andreas Burkert

The evolution of a giant planet within the stellar envelope of a main-sequence star is investigated as a possible mechanism for enhancing the stellar metallicities of the parent stars of extrasolar planetary systems. Three-dimensional hydrodynamical simulations of a planet subject to impacting stellar matter indicate that the envelope of a Jupiter-like giant

Michael Kramer

New observations of the binary pulsar B1913+16 are presented. Since 1978 the leading component of the pulse profile has weakend dramatically by about 40%. For the first time, a decrease in component separation is observed, consistent with expectations of geodetic precession. Assuming the correctness of general relativity and a circular hollow-cone like beam,

Jeremy S. Heyl, Lars Hernquist

Recently launched x-ray telescopes have discovered several candidate isolated neutron stars. The thermal radiation from these objects may potentially constrain our understanding of nuclear physics in a realm inaccessible to terrestrial experiments. To translate the observed fluxes from neutron stars into constraints, one needs precise calculations of the hea

Heinz Andernach

I review some of the past and current methods for retrieval of literature and other published information, excluding commercial services. Much of this is a personal view and based on experience made at various institutions, some of them neither with an adequately complete astronomy library, nor with a professional astronomy librarian. Rather than describing

Luis C. Ho

Many nearby early-type (elliptical and S0) galaxies contain weak (milli-Jansky level) nuclear radio sources on scales a few hundred parsecs or less. The origin of the radio emission, however, has remained unclear, especially in volume-limited samples that select intrinsically less luminous galaxies. Both active galactic nuclei and nuclear star formation have

L. Nicastro, L. Amati, L. A. Antonelli, R. C. Butler

GRB970402 is the fourth gamma-ray burst detected by BeppoSAX simultaneously in the Gamma Ray Burst Monitor (GRBM) and one of the two Wide Field Cameras (WFCs). A rapid pointing of the BeppoSAX Narrow Field Instruments (NFIs) 8 hours after the GRB led to the identification of an unknown weak X-ray source: 1SAX J1450.1-6920. Its position was approximately at t

David Bennett

I review recent results from gravitational microlensing surveys of the Large Magellanic Cloud. The combined microlensing optical depth of the MACHO and EROS-1 surveys is tau_LMC = 2.1{+1.3/-0.8}* 10^{-7} which is substantially larger than the background of tau < 0.5* 10^{-7} from lensing by known stars but is below the expected microlensing optical depth of

Koji Uryu, Yoshiharu Eriguchi

Circularly orbiting black hole-gaseous star close binary systems are examined by using numerically exact stationary configurations in the framework of Newtonian gravity. We have chosen a polytropic star for the fluid component of the binary system and considered two ideal situations: 1) a synchronously rotating star and 2) an irrotationally rotating star. Th

Koji Uryu, Yoshiharu Eriguchi

We propose a new numerical method to calculate irrotational binary systems composed of compressible gaseous stars in Newtonian gravity. Assuming irrotationality, i.e. vanishing of the vorticity vector everywhere in the star in the inertial frame, we can introduce the velocity potential for the flow field. Using this velocity potential we can derive a set of

Munhwan Gim, Don. A. VandenBerg, Peter B. Stetson, James E. Hesser

A (V,V - I)--diagram for the intermediate-age open cluster NGC 7789 has been derived from CCD observations of more than 15,000 stars within ~ 18 arcmin of the cluster center. From the brightest giants and blue stragglers at V ~ 11 to the faintest lower main-sequence stars that were observed (at V ~ 21, M_V ~ 9), the C-M diagram is well defined. A prominent c

R. G. Gratton, E. Carretta, G. Clementini

We discuss the impact of Population II and Globular Cluster (GCs) stars on the derivation of the age of the Universe, and on the study of the formation and early evolution of galaxies, our own in particular. The long-standing problem of the actual distance scale to Population II stars and GCs is addressed, and a variety of different methods commonly used to

Romain Teyssier, Jean-Pierre Chieze, Jean-Michel Alimi

We investigate the influence of non equilibrium thermodynamics on cosmological structure formation. In this paper, we consider the collapse of planar perturbations usually called &#34;Zel&#39;dovich pancakes&#34;. We have developed for that purpose a new two fluids (gas and dark matter) hydrodynamical code, with three different thermodynamical species: elect

Thomas Kunzl, Harald Lesch, Axel Jessner

We calculate the beaming of coherent emission by means of geometrical optics. When spherical elementary waves are phase-coupled in that way that constructive interference occurs along one axis, the intensity is lower for off-axis viewing angles. The spatial angle of constructive interference shrinks to a fraction of $4π$ when the length scale of the emission

J. G. Kirk, Lewis Ball, Olaf Skjaeraasen

We derive light curves for the hard gamma-ray emission, at energies up to several TeV, expected from the unique pulsar/Be-star binary system PSR B1259-63. This is the only known system in our galaxy in which a radio pulsar is orbiting a main sequence star. We show that inverse Compton emission from the electrons and positrons in the shocked pulsar wind, scat

Pervez Hoodbhoy, Xiangdong Ji, Wei Lu

We study the chromodynamical gauge symmetry in relation to the internal spin structure of the nucleon. We show that 1) even in the helicity eigenstates the gauge-dependent spin and orbital angular momentum operators do not have gauge-independent matrix element; 2) the evolution equations for the gluon spin take very different forms in the Feynman and axial g

F. W. Stecker, M. H. Salamon

We present the results of a new calculation of the photodisintegration of ultrahigh energy cosmic ray (UHCR) nuclei in intergalactic space. The critical interactions for energy loss and photodisintegration of UHCR nuclei occur with photons of the 2.73K cosmic background radiation (CBR) and with photons of the infrared background radiation (IBR). We have reex

Jorge Gamboa, Mikhail Plyushchay, Jorge Zanelli

Recently it was observed by one of the authors that supersymmetric quantum mechanics (SUSYQM) admits a formulation in terms of only one bosonic degree of freedom. Such a construction, called the minimally bosonized SUSYQM, appeared in the context of integrable systems and dynamical symmetries. We show that the minimally bosonized SUSYQM can be obtained from

M. E. Dodd, P. C. Hendry, N. S. Lawson, P. V. E. McClintock

A new experiment has been performed to study the formation of topological defects (quantized vortices) during rapid quenches of liquid 4He through the superfluid transition, with particular care taken to minimise vortex creation via conventional hydrodynamic flow processes. It is found that the generated vortices, if any, are being produced at densities at l

Michael B. Green, Savdeep Sethi

Supersymmetry is used to derive conditions on higher derivative terms in the effective action of type IIB supergravity. Using these conditions, we are able to prove earlier conjectures that certain modular invariant interactions of order alpha&#39; **3 relative to the Einstein-Hilbert term are proportional to eigenfunctions of the Laplace operator on the fun

Otto C. W. Kong

Focusing on a simple three neutrino oscillation scenario motivated by the recent Super-Kamiokande result, we discuss both tree-level and 1-loop contributions to neutrino masses in supersymmetry without R-parity, aiming at discerning the flavor structure issues of the theory. The single-VEV parametrization framework, which allows the first consistent treatmen

Rennan Barkana, Joseph Lehar, Emilio E. Falco, Norman A. Grogin

We examine models of the mass distribution for the first known case of gravitational lensing. Several new sets of constraints are used, based on recent observations. We remodel the VLBI observations of the radio jets in the two images of Q0957+561, showing that the previously derived positions and uncertainties were incorrect. We use as additional constraint

R. N. Mohapatra, S. Nussinov

The recently announced Super-Kamiokande data on atmospheric neutrino oscillation seems to require a maximal mixing between the $ν_μ$ and $ν_τ$ within the conventional three neutrino picture. It is then tempting to suggest as has been done in literature, that the solar neutrino deficit be also understood as resulting from a maximal mixing between $ν_e$ and $ν

Howard Georgi, S. L. Glashow

Recent data lead us to a simple and intriguing form of the neutrino mass matrix. In particular, we find solar neutrino oscillations to be nearly maximal (and rule out the small-angle MSW explanation of solar neutrino observations) if relic neutrinos comprise at least one~percent of the critical mass density of the universe.

Ren-Jie Zhang

We calculate a two-loop effective potential to the order of {\cal O}(λ_t^2α_s) in the MSSM. We then study the corresponding two-loop corrections to the CP-even Higgs-boson mass for arbitrary \tanβand left-right top-squark mixings. We find that the lightest Higgs-boson mass is changed by at most a few GeV. We also show the improved scale dependence and compar

I. Barabanov, P. Belli, R. Bernabei, V. I. Gurentsov

Some electroweak models with extended neutral currents, such as those based on the $E_6$ group, lead to an increase of the $\barν-e$ scattering cross section at energies below 100 keV. We propose to search for the heavy Z&#39; boson contribution in an experiment with a high-activity artificial neutrino source and with a large-mass detector. We present the ca

P. Meszaros, M. J. Rees, R. A. M. J. Wijers

A wide range of mechanisms have been proposed to supply the energy for gamma-ray bursts (GRB) at cosmological distances. It is a common misconception that some of these, notably NS-NS mergers, cannot meet the energy requirements suggested by recent observations. We show here that GRB energies, even at the most distant redshifts detected, are compatible with

Scott F. Anderson, Craig J. Hogan, Benjamin F. Williams, Robert F. Carswell

We present a new HST/STIS spectrum of the z=3.18 quasar PKS 1935-692 and summarize the spectral features shortwards of 304A in the rest frame likely to be caused by foreground HeII Lyman-alpha absorption. In accord with previous results on two other quasars at similar redshifts, we demonstrate a correlation with the HI Lyman-alpha forest absorption, and show

S. Davidson, S. F. King

We discuss neutrino masses in the framework of a minimal extension of the minimal supersymmetric standard model (MSSM) consisting of an additional single right-handed neutrino superfield $N$ with a heavy Majorana mass $M$, which induces a single light see-saw mass $m_{ν_3}$ leaving two neutrinos massless at tree-level. This trivial extension to the MSSM may

P. E. Kornilovitch, Bumsoo Kyung

Angle-resolved photoemission spectra are calculated microscopically for the two-dimensional attractive Hubbard model. A system of self-consistent T-matrix equations are solved numerically in the real-time domain. The single-particle spectral function has a two-peak structure resulting from the presense of bound states. The spectral function is suppressed at

B. Kleihaus

The electroweak model is extended by a second Higgs doublet and a numerical investigation of static, finite energy classical solutions is performed. The results indicate that for a large domain of the parameters of the Higgs potential, the energy barrier between topologically distinct vacua of the Lagrangian is constituted by a bisphaleron.

H. -T. Janka, G. G. Raffelt

In a supernova core, magnetic fields cause a directional variation of the neutrino refractive index so that resonant flavor oscillations would lead to a deformation of the &#34;neutrinosphere&#34; for, say, tau neutrinos. The associated anisotropic neutrino emission was proposed as a possible origin of the observed pulsar proper motions. We argue that this e

A. Fix, I. Glavanakov, Yu. Krechetov

Reactions A(γ, pi^+p) are considered to proceed through the formation of pion-proton pairs on delta constituents in nuclei. We develop the nonrelativistic operator for Δ^{++}(γ, pi^+)p process in an arbitrary frame. The calculated cross section for C12(γ, π^+p) reaction is compared to the existing experimental data.

Giovanni Amelino-Camelia

As a consequence of the extreme precision of the measurements it performs, an interferometric gravitational wave detector is a macroscopic apparatus for which quantum effects are not negligible. I observe that this property can be exploited to probe some aspects of the interplay between Quantum Mechanics and Gravity.

M. Ortuno, E. Cuevas

We show by a numerical procedure that a short-range interaction $u$ induces extended two-particle states in a two-dimensional random potential. Our procedure treats the interaction as a perturbation and solve Dyson&#39;s equation exactly in the subspace of doubly occupied sites. We consider long bars of several widths and extract the macroscopic localization

N. V. Antonov

The field theoretic renormalization group (RG) is applied to the problem of a passive scalar advected by the Gaussian self-similar velocity field with finite correlation time and in the presence of an imposed linear mean gradient. The energy spectrum in the inertial range has the form $E(k)\propto k^{1-ε}$, and the correlation time at the wavenumber k scales

Anthony Chefles, Stephen M. Barnett

Unambiguous discrimination and exact cloning reduce the square-overlap between quantum states, exemplifying the more general type of procedure we term state separation. We obtain the maximum probability with which two equiprobable quantum states can be separated by an arbitrary degree, and find that the established bounds on the success probabilities for dis

Villain Pierre, Lewenstein Maciej

We study the dynamics of the relative phase between two Bose-Einstein condensates coupled via collisions and via a Josephson-like coupling. We derive the equations of the motion for the relative phase and the relative number operators from the second quantized Hamiltonian of the system using a quantum field theoretical approach. We distinguish the cases in w

C. B. Muratov, V. V. Osipov

We discovered a new type of spiral wave solutions in reaction-diffusion systems --- spike spiral wave, which significantly differs from spiral waves observed in FitzHugh-Nagumo-type models. We present an asymptotic theory of these waves in Gray-Scott model. We derive the kinematic relations describing the shape of this spiral and find the dependence of its m

Peter. C. Tandy

We illustrate the progress of covariant QCD phenomenology for the description of meson coupling constants and form factors. As examples, we discuss the $ρππ$ and $γπρ$ interactions, the $ρ$ contribution to the pion charge radius, and the $ρNN$ and $ωNN$ vector and tensor coupling constants and form factors.

H. W. Barz

Correlations of two like charged pions emitted from a hot and charged spherically expanding nuclear system are investigated. The motion of the pions is described quantum mechanically using the Klein-Gordon equation which includes Coulomb field and pion absorption. Flow modifies the radial distribution of the source function and rescales the pion wave functio

J. Meng, K. Sugawara-Tanabe, S. Yamaji, A. Arima

Based on the Relativistic continuum Hartree-Bogoliubov (RCHB) theory, the pseudo-spin approximation in exotic nuclei is investigated in Zr and Sn isotopes from the proton drip line to the neutron drip line. The quality of the pseudo-spin approximation is shown to be connected with the competition between the centrifugal barrier (CB) and the pseudo-spin orbit

D. E. Kahana, S. H. Kahana

We reexamine the production of J/Psi and other charmonium states for a variety of target-projectile choices at the SPS. For this study we use a newly constructed cascade code LUCIFER II, which yields acceptable descriptions of both hard and soft processes, specifically Drell-Yan and hidden charm production, and soft energy loss and meson production, at the S

Cs. Anderlik, Zs. I. Lázár, V. K. Magas, L. P. Csernai

In fluid dynamical models the freeze out of particles across a three dimensional space-time hypersurface is discussed. The calculation of final momentum distribution of emitted particles is described for freeze out surfaces, with both space-like and time-like normals, taking into account conservation laws across the freeze out discontinuity.

012 Collaboration, C. Bochna, B. P. Terburg et al

The first measurements of the differential cross section for the d(gamma,p)n reaction up to 4.0 GeV were performed at Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. We report the cross sections at the proton center-of-mass angles of 36, 52, 69 and 89 degrees. These results are in reasonable agreement with previous measurements at low

A. A. Donkov, A. D. Donkov, E. I. Grancharova

Some multidimensional generalizations of the Fokker-Planck equation used by R. Friedrich and J. Peinke for the description of a turbulent cascade as a stochastic process of Markovian type, are considered. The exact solutions of the Cauchy problems for these equations are found with the operator methods.

Thomas H. Otway

A version of the nonlinear Hodge equations is introduced in which the irrotationality condition is weakened. An elliptic estimate for solutions is derived.

Jimmy Petean

For a compact connected manifold M of dimension n greater than 3 and with no metric of positive scalar curvature, we prove that the Yamabe invariant is unchanged under surgery on spheres of dimension different from 1, n-2 and n-1. We use this result to give new computations of the invariant in dimension four and display new examples of 4-manifolds which do n

Jimmy Petean, Gabjin Yun

We study the Yamabe invariant of manifolds obtained as connected sums along submanifolds of codimension greater than 2. In particular, given a compact smooth manifold M which does not admit metrics of positive scalar curvature, we prove that the Yamabe invariant of M is an upper bound for the Yamabe invariant of any manifold obtained by performing surgery in

Rick Vaughn

The generalized soap bubble problem seeks the least perimeter way to enclose and separate n given volumes in R^m. We study the possible configurations for perimeter minimizing bubble complexes enclosing more than two regions. We prove that perimeter minimizing planar bubble complexes with equal pressure regions and without empty chambers must have connected

L. Lapointe, A. Lascoux, J. Morse

We show that the action of classical operators associated to the Macdonald polynomials on the basis of Schur functions, S_λ[X(t-1)/(q-1)], can be reduced to addition in λ-rings. This provides explicit formulas for the Macdonald polynomials expanded in this basis as well as in the ordinary Schur basis, S_λ[X], and the monomial basis, m_λ[X].

D. Shklyarov, S. Sinel&#39;shchikov, L. Vaksman

In our earlier work math.QA/9808015 some results on integral representations of functions in quantum disc were announced. It was then shown in math.QA/9808037 that the validity of those results is related to the invariance of kernels of some integral operators. We introduce here a method which allows us to prove the invariance of the above kernels.

Tahl Nowik

Let GI denote the space of all generic immersions of a surface F into a 3-manifold M. Let q(H_t) denote the number mod 2 of quadruple points of a generic regular homotopy H_t : F -> M. We are interested in defining an invariant Q : GI -> Z/2 such that q(H_t) = Q(H_0) - Q(H_1) for any generic regular homotopy H_t : F -> M. Such an invariant exists iff q=0 for

Ivan Dimitrov, Ivan Penkov

In this article we initiate a systematic study of irreducible weight modules over direct limits of reductive Lie algebras, and in particular over the simple Lie algebras $A(\infty)$, $B(\infty)$, $C(\infty)$ and $D(\infty)$. Our main tool is the shadow method introduced recently in \cite{DMP}. The integrable irreducible modules are an important particular cl

Oleg V. Goodyckov

Here is present short proofing of Jordan&#39;s theorem about dividing of flat on two disjoint subsets by one closed curve.

Xavier Buff

We show that the Feigenbaum-Cvitanovic equation can be interpreted as a linearizing equation, and the domain of analyticity of the Feigenbaum fixed point of renormalization as a basin of attraction. There is a natural decomposition of this basin which enables to recover a result of local connectivity by Jiang and Hu for the Feigenbaum Julia set.

J. A. Harvey, R. Minasian, G. Moore

We use the anomaly cancellation of the M-theory fivebrane to derive the R-symmetry anomalies of the $A_{N}$ $(0,2)$ tensor-multiplet theories. This result leads to a simple derivation of black hole entropy in $d=4, \mathcal{N}=2$ compactifications of $M$-theory. We also show how the formalism of normal bundle anomaly cancellation clarifies the Kaluza-Klein o

T. Dereli, Robin W. Tucker

The Cremmer-Scherk mechanism is generalised in a non-Abelian context. In the presence of the Higgs scalars of the standard model it is argued that fields arising from the low energy effective string action may contribute to the mass generation of the observed vector bosons that mediate the electroweak interactions and that future analyses of experimental dat

Subir Ghosh

Bosonisation of the massive Thirring model, with a non-minimal and non-abelian gauging is studied in 2+1-dimensions. The static abelian model is solved completely in the large fermion mass limit and the spectrum is obtained. The non-abelian model is solved for a restricted class of gauge fields. In both cases explicit expressions for bosonic currents corresp

Bayram Tekin, Kamran Saririan, Yutaka Hosotani

In this talk, we give a brief discussion of complex monopole solutions in the three dimensional Georgi-Glashow model with a Chern-Simons term. We find that there exist complex monopole solutions of finite action. They dominate the path integral and disorder the Higgs vacuum, but electric charges are not confined. Subtleties in the model and issues related to

M. Suzuki

The updated experimental data are used to analyze the final-state interaction phases of the two-body decay amplitudes of the B mesons. Combining the upper bounds on the branching fractions of the color-suppressed modes with those of the charged modes, we have set constraints on the relative phases between the amplitudes $A(B^0 \to X^- Y^+)$ and $A(B^+ \to X^

S. Chang, C. Hagmann, P. Sikivie

We discuss the decay of axion walls bounded by strings and present numerical simulations of the decay process. In these simulations, the decay happens immediately, in a time scale of order the light travel time, and the average energy of the radiated axions is $<ω_a > \simeq 7 m_a$ for $v_a/m_a\simeq 500$. $<ω_a>$ is found to increase approximately linearly

D. de Florian, R. Sassot

We present a combined QCD analysis of diffractive and leading proton deep inelastic scattering data using the framework of fracture functions. It is shown that this framework allows a precise and unified perturbative QCD description for the data, alternative to those that relay on Regge factorization.

C. T. Traxler, U. Mosel, T. S. Biro

We have carried out simulations of the hadronization of a hot, ideal but effectively massive quark-gluon gas into color neutral clusters in the framework of the semi-classical SU(3) chromodielectric model. We have studied the possible quark-gluon compositions of clusters as well as the final mass distribution and spectra, aiming to obtain an insight into rel

A. Abada, J. Matias, R. Pittau

In this paper, we compute the Standard Model polarized amplitudes and cross sections of the processes $γν\toγγν$, $γγ\to γν\barν$ and $ν\barν\to γγγ$, for centre-of-mass energies $ω$ within the range of validity of the Fermi theory. By using a large electron-mass expansion of the exact result, we also derive the first correction term to the effective, low-en

J. W. F. Valle

Bilinear R-parity violation (BRpV) provides the simplest and most meaningful way to include such effects into the Minimal Supersymmetrical Standard Model (MSSM). It is defined by a quadratic superpotential term $εL H$ which mixes lepton and Higgs superfields and mimics the effects of models with spontaneous breaking. I review some of its main features and sh

S. Glenn

Using a data sample collected with the CLEO II detector at CESR, we have searched for dipion transitions between pairs of $Υ$ resonances at energies near the $Υ(4S)$. We obtain upper limits $B(Υ(4S)\to Υ(2S)π^+π^-) < 3.9 \times 10^{-4}$ and $B(Υ(4S)\to Υ(1S)π^+π^-) < 1.2 \times 10^{-4}$. We also observe the transitions $Υ(3S)\to Υ(1S)$, $Υ(3S)\to Υ(2S)$, and

Z. C. Wu

The concept of constrained gravitational instanton is introduced. It is used to study black hole creation. We discussed the global aspects of the scenario and the alternative tunnelings.

Jeeva Anandan

The quantum measurement problem and various unsuccessful attempts to resolve it are reviewed. A suggestion by Diosi and Penrose for the half life of the quantum superposition of two Newtonian gravitational fields is generalized to an arbitrary quantum superposition of relativistic, but weak, gravitational fields. The nature of the ``collapse&#39;&#39; proces

Alberto Saa

We show that Raychaudhuri&#39;s recently proposed theorem on nonrotating universes cannot be used to rule out realistic singularity-free descriptions of the universe, as suggested by him in PRL 80, 654 (1998).

Daksh Lohiya, Annu Batra, Shobhit Mahajan, Amitabha Mukherjee

Primordial nucleosynthesis is considered a success story of the standard big bang (SBB) cosmology. The cosmological and elementary particle physics parameters are believed to be severely constrained by the requirement of correct abundances of light elements. We explore nucleosynthesis in a class of models very different from SBB. In these models the cosmolog

Ion I. Cotăescu

We show that the Dirac equation on de Sitter background can be analytically solved in a special static frame where the energy eigenspinors can be expressed in terms of usual angular spinors known from special relativity, and a pair of radial wave functions.

Frank Antonsen

We study the deformation quantisation (Moyal quantisation) of general constrained Hamiltonian systems. It is shown how second class constraints can be turned into first class quantum constraints. This is illustrated by the O(N) non-linear $σ$-model. Some new light is also shed on the Dirac bracket. Furthermore, it is shown how classical constraints not in in

Steven R. White, Richard L. Martin

In this paper we describe how the density matrix renormalization group (DMRG) can be used for quantum chemical calculations for molecules, as an alternative to traditional methods, such as configuration interaction or coupled cluster approaches. As a demonstration of the potential of this approach, we present results for the H$_2$O molecule in a standard gau

E. Miranda, V. Dobrosavljevic

We investigate the role of localization effects in the Kondo disorder mechanism for non-Fermi liquid behavior in disordered Kondo lattices. We find that the distribution of Kondo temperatures is strongly affected by fluctuations of the conduction electron density of states, a feature neglected in the previous treatment. For moderate disorder, the self-consis

S. -K. Yip

In this paper I study the energy resolved supercurrent of a junction consisting of a dirty normal metal between two superconductors. I also consider a cross geometry with two additional arms connecting the above mentioned junction with two normal reservoirs at equal and opposite voltages. The dependence of the supercurrent between the two superconductors on

Claudia Filippi, David M. Ceperley

Recent high resolution Compton scattering experiments in lithium have shown significant discrepancies with conventional band theoretical results. We present a pseudopotential quantum Monte Carlo study of electron-electron and electron-ion correlation effects on the momentum distribution of lithium. We compute the correlation correction to the valence Compton

I. Campillo, J. M. Pitarke, A. G. Eguiluz

Ab initio calculations of the electronic energy loss of ions moving in aluminum crystal are presented, within linear-response theory, from a realistic description of the one-electron band-structure and a full treatment of the dynamical electronic response of valence electrons. For the evaluation of the density-response function we use the random-phase approx

Ming Li, Brian B. Smith, Robin L. B. Selinger

We identify a fundamental morphological instability of mobile dislocations in crystals and related line defects. A positive gradient in the local driving force along the direction of defect motion destabilizes long-wavelength vibrational modes, producing a ``fingering&#39;&#39; pattern. The minimum unstable wavelength scales as the inverse square root of the

Y. N. Skryabin, A. V. Chukin

The small-angle scattering of neutrons on large scale inhomogeneities of two-component systems in refraction range is considered. We supposed, that neutrons acquire phase shifts describing by the Gaussian distribution function. It is shown that the average cross section of scattering contains two contributions. The first contribution describes the diffractio

Erik Koch, Olle Gunnarsson, Richard M. Martin

Fullerides are crystals made from C60 molecules. When doped with alkali metals the valence electrons of the alkali atoms are transfered to the C60 molecules. We show how to set up a model Hamiltonian to describe the correlated hopping of these electrons between C60 molecules. Then we discuss Monte Carlo methods for such lattice Hamiltonians, putting special

A. Avella, F. Mancini, D. Villani

We comment on the Reply of G. Su and M. Suzuki [cond-mat/9808011] to our Comment [cond-mat/9807402] about the papers of G. Su [Phys. Rev. B 54, 8291 (1996)] and G. Su and M. Suzuki [Phys. Rev. B 57, 13367 (1998)]. The algebraic mistake originating their incorrect solutions is evidenced in detail.

A. R. Hamilton, M. Y. Simmons, M. Pepper, E. H. Linfield

We report the observation of a re-entrant insulator--metal--insulator transition at B=0 in a two dimensional (2D) hole gas in GaAs at temperatures down to 30mK. At the lowest carrier densities the holes are strongly localised. As the carrier density is increased a metallic phase forms, with a clear transition at σ= ~5e^2/h. Further increasing the density wea

C. Kilic, H. Mehrez, S. Ciraci

The conductance through a quantum point contact created by a sharp and hard metal tip on the graphite surface has features which to our knowledge have not been encountered so far in metal contacts or in nanowires. In this paper we first investigate these features which emerge from the strongly directional bonding and electronic structure of graphite, and pro

Daniel L. Miller

In this work we show that the Anderson impurity model applied to ``scar&#39;&#39; wave function may explain large fluctuations of ground state energy of electron gas in a quantum dot.

Nam Kim, Yong Joo Doh, Hyun-Sik Chang, Hu-Jong Lee

We fabricated small-size stacks on the surface of Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ (BSCCO-2212) single crystals with the bulk transition temperature $T_c$$\simeq$90 K, each containing a few intrinsic Josephson junctions. Below a critical temperature $T_c&#39;$ ($\ll$ $T_c$), we have observed a weakened Josephson coupling between the CuO$_2$ superconducting doub

Xavier Leoncini, Alberto D. Verga

The paper has been withdrawn.

M. del Mar Espinosa, Miguel A. Martin-Delgado, Alfonso Niella, David Paramo

The behaviour of an electron in a potential that resembles that of a bidimensional solid with a perpendicular magnetic field applied is studied from a classical point of view. This problem presents the standard features of chaos and some interesting new patterns. A new chaos indicator, called random walk indicator, is presented to describe som of these new p

Andrew J. Bunker, Francine R. Marleau, James R. Graham

We describe the initial results of a deep long-slit emission line search for redshifted (2.7<z<4.1) Lyman-alpha. These observations are used to constrain the fluorescent Ly-alpha emission from the population of clouds whose absorption produces the higher-column-density component of the Ly-alpha forest in quasar spectra. We use the results to set an upper lim

D. T. Frayer, R. J. Ivison, N. Z. Scoville, M. Yun

We report the detection of CO(3-2) emission from the submillimeter-selected hyperluminous galaxy SMM 02399-0136. This galaxy is the brightest source detected in the recent SCUBA surveys of the submillimeter sky. The optical counterpart of the submillimeter source has been identified as a narrow-line AGN/starburst galaxy at z=2.8. The CO emission is unresolve

Roger Angel, Jim Burge

The lightweighting and surface accuracy targeted for NGST&#39;s 8 m primary mirror has been demonstrated in a 0.5 m prototype. Now a second, 2 m prototype weighing 40 kg in total is being fabricated at the University of Arizona under the NGST NMSD program. It will be tested in cryogenic operation in spring 1999. A third, advanced mirror system demonstrator (

Gary J. Ferland

The Orion Nebula is the defining galactic HII Region, and has been well studied over a broad range of wavelengths. The gas-phase metallicity is 2/3 of solar, close to the star cluster. Grains survive throughout. The Trapezium cluster&#39;s radiation field will drive the dusty gas away, pushing it back against the photodissociation region (PDR). The nebula is

Luis N. Epele, Esteban Roulet

We study the propagation of ultra-high energy cosmic ray nuclei through the background of cosmic microwave and intergalactic infrared photons, using recent re-estimates for the density of the last ones. We perform a detailed Monte Carlo simulation to follow the disintegration histories of nuclei starting as Fe and reaching the Earth from extragalactic source

Frank C. Jones, J. Randy Jokipii, Matthew G. Baring

We give a rigorous derivation of a theorem showing that charged particles in an arbitrary electromagnetic field with at least one ignorable spatial coordinate remain forever tied to a given magnetic-field line. Such a situation contrasts the significant motions normal to the magnetic field that are expected in most real three-dimensional systems. It is point

Koji Uryu, Yoshiharu Eriguchi

In this paper we have examined numerically exact configurations of close binary systems composed of incompressible fluids with internal flows. Component stars of binary systems are assumed to be circularly orbiting each other but rotating nonsynchronously with the orbital motion, i.e. stars in binary systems have steady motions seen from a rotational frame o

David A. Neufeld, Gary J. Melnick, Martin Harwit

We have detected the S(1), S(2), S(3), S(4) and S(5) pure rotational lines of molecular hydrogen toward the outflow source HH 54, using the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO). The observed H2 line ratios indicate the presence of warm molecular gas with an H2 density of at least 100,000 per cubic centimeter and a

Arnon Dar, Giora Shaviv

The $^8$B solar neutrino flux as measured by Super-Kamiokande is consistent with the $^{37}$Ar production rate in $^{37}$Cl at Homestake. GALLEX and SAGE, continue to observe $^{71}$Ge production rates in $^{71}$Ga that are consistent with the minimal signal expected from the solar luminosity. The observed $^8$B solar neutrino flux is in good agreement with

Hsiang-Kuang Chang, Cheng Ho

PSR B0656+14 was observed by the {\it Rossi X-ray Timing Explorer (RXTE)} with the proportional counter array (PCA) and the high-energy x-ray timing experiment (HEXTE) for 160 ksec during August 22 -- September 3, 1997. No pulsation was firmly found in the timing analysis, in which the contemporaneous radio ephemeris and various statistical tests were applie

G. Moriondo, R. Giovanelli, M. P. Haynes

We study the correlations with inclination of H-band disk and bulge structural parameters and I-H colour profiles for a sample of 154 spiral galaxies, in order to detect possible effects due to internal extinction by dust. The selection of the sample assures that galaxies at different inclinations are not intrinsically different, so that the observed correla