March 1998 arXiv papers — page 13

Anzhong Wang, Yumei Wu

A large family of solutions, representing, in general, spherically symmetric Type II fluid, is presented, which includes most of the known solutions to the Einstein field equations, such as, the monopole-de Sitter-charged Vaidya ones.

Simon Davis

Several arguments are given for the summability of the superstring perturbation series. Whereas the Schottky group coordinatization of moduli space may be used to provide refined estimates of large-order bosonic string amplitudes, the super-Schottky group variables define a measure for the supermoduli space integral which leads to upper bounds on superstring

J. V. Alvarez, J. González

We apply a wilsonian renormalization group approach to the continuum limit of the attractive $t-t'$ Hubbard model, taken when the Fermi level is at the Van Hove singularity of the density of states. The model has well-defined scaling properties and the effective couplings display an unbounded flow in the infrared. We determine the leading instabilities b

Nick E. Mavromatos, Richard J. Szabo

We establish conditions under which the worldsheet beta-functions of logarithmic conformal field theories can be derived as the gradient of some scalar function on the moduli space of running coupling constants. We derive a renormalization group invariant version of this function and relate it to the usual Zamolodchikov C-function expressed in terms of corre

Takashi Kimura, Hiroki Saito, Masahito Ueda

It is found that combining an excitation-energy sum rule with Fetter's trial wave function gives almost exact low-lying collective-mode frequencies of a trapped Bose-Einstein condensate at zero temperature.

Takao Morinari

We discuss the possibility of the quantum Hall effect at half-filled Landau level in terms of the pairing of the composite fermions. In the absence of Coulomb energy, we show that the ground state of the system is described by the {\it p}-wave BCS pairing state of composite fermions. When the ratio $α\equiv (e^2/ε\ell_B)/ε_F$ ($\ell_B$ : the magnetic length,

E. Bergshoeff, K. Behrndt

The large N limit of D3-branes is expected to correspond to a superconformal field theory living on the boundary of the anti-de Sitter space appearing in the near-horizon geometry. Dualizing the D3-brane to a D-instanton, we show that this limit is equivalent to a type IIB S-duality. In both cases one effectively reaches the near-horizon geometry. This provi

Wen-Xiu Ma

A Hamiltonian pair with arbitrary constants is proposed and thus a sort of hereditary operators is resulted. All the corresponding systems of evolution equations possess local bi-Hamiltonian formulation and a special choice of the systems leads to the KdV hierarchy. Illustrative examples are given.

Igor Halperin, Ariel Zhitnitsky

We generalize the large N_c Di Vecchia-Veneziano-Witten (VVW) effective chiral Lagrangian to the case of finite N_c by constructing the anomalous effective Lagrangian for QCD. The latter is similar to its SUSY counterpart, and has a holomorphic structure. The VVW construction is then recovered, along with 1/N_c corrections, after integrating out the heavy &#

Gustavo Dotti, Aneesh V. Manohar, Witold Skiba

We study the low-energy dynamics of all N=1 supersymmetric gauge theories whose basic gauge invariant fields are unconstrained. This set includes all theories whose matter Dynkin index is less than the index of the adjoint representation. We study the dynamically generated superpotential in these theories, and show that there is a W=0 branch if and only if a

S. Ahmad, B. E. Bonner, S. V. Efremov, G. S. Mutchler

The double differential multiplicities and rapidity distributions for Lambda hyperon production in central Au+Au interactions at AGS in the range of rapidities from 1.7 to 3.2 and the range of transverse kinetic energies from 0.0 to 0.7 GeV are parametrized in terms of the the Blast Wave approximation. The longitudinal and transverse radial expansion paramet

Jeremy Kepner, Xiaohui Fan, Neta Bahcall, James Gunn

We describe an automated method for detecting clusters of galaxies in imaging and redshift galaxy surveys. The Adaptive Matched Filter (AMF) method utilizes galaxy positions, magnitudes, and---when available---photometric or spectroscopic redshifts to find clusters and determine their redshift and richness. The AMF can be applied to most types of galaxy surv

B. E. King, C. S. Wood, C. J. Myatt, Q. A. Turchette

We report preparation in the ground state of collective modes of motion of two trapped 9Be+ ions. This is a crucial step towards realizing quantum logic gates which can entangle the ions' internal electronic states. We find that heating of the modes of relative ion motion is substantially suppressed relative to that of the center-of-mass modes, suggestin

P. P. Avelino, E. P. S. Shellard, J. H. P. Wu, B. Allen

We investigate the non-gaussian properties of cosmic-string-seeded linear density perturbations with cold and hot dark matter backgrounds, using high-resolution numerical simulations. We compute the one-point probability density function of the resulting density field, its skewness, kurtosis, and genus curves for different smoothing scales. A semi-analytic m

Georg Junker, Pinaki Roy

We present in this paper a rather general method for the construction of so-called conditionally exactly solvable potentials. This method is based on algebraic tools known from supersymmetric quantum mechanics. Various families of one-dimensional potentials are constructed whose corresponding Schrödinger eigenvalue problem can be solved exactly under certain

M. G. Moore, P. Meystre

We formulate a wave atom optics theory of the Collective Atomic Recoil Laser, where the atomic center-of-mass motion is treated quantum mechanically. By comparing the predictions of this theory with those of the ray atom optics theory, which treats the center-of-mass motion classically, we show that for the case of a far off-resonant pump laser the ray optic

D. Han, Y. S. Kim

It is shown that the SU(1,1)-like and SU(2)-like two-photon coherent states can be combined to form a O(3,2)-like two-photon states. Since the O(3,2) group has many subgroups, there are also many new interesting new coherent and squeezed two-photon states. Among them is the two-photon sheared state whose symmetry property is like that for the two-dimensional

X. Z. Tang, A. H. Boozer

We consider the design criteria of a chemical mixing device based on a chaotic flow, with an emphasis on the steady-state devices. The merit of a reactor, defined as the $Q$-factor, is related to the physical dimension of the device and the molecular diffusivity of the reactants through the local Lyapunov exponents of the flow. The local Lyapunov exponent ca

M. Blaauboer, A. G. Kofman, A. E. Kozhekin, G. Kurizki

We theoretically investigate the response of optical phase conjugators to incident probe pulses. In the stable (sub-threshold) operating regime of an optical phase conjugator it is possible to transmit probe pulses with a superluminally advanced peak, whereas conjugate reflection is always subluminal. In the unstable (above-threshold) regime, superluminal re

Gabriel Martinez-Pinedo, Petr Vogel

The nucleus 54Mn has been observed in cosmic rays. In astrophysical environments it is fully stripped of its atomic electrons and its decay is dominated by the beta- branch to the 54Fe ground state. Application of 54Mn based chronometer to study the confinement of the iron group cosmic rays requires knowledge of the corresponding halflife, but its measuremen

Steven N. Evans

These are lecture notes from a course given at the CRM in Montreal in 1992. They survey the author's attempts to find and understand canonical probabilistic entities in a local field (e.g. p-adic) setting. We propose answers to the related questions: ``What are the analogues for Gaussian measures?'' and ``What are the analogues for Brownian motio

Feng Xu

We prove a conjecture of Zuber on the signature of intersection froms associated with affine algebras of type A.

Keiko Kawamuro

First, we construct the Jones tower and tunnel of the central sequence subfactor arising from a hyperfinite type II_1 subfactor with finite index and finite depth, and prove each algebra has the double commutant property in the ultraproduct of the enveloping II_1 factor. Next, we show the equivalence between Popa's strong amenability and the double commu

J. Denef, F. Loeser

We define motivic analogues of Igusa's local zeta functions. These functions take their values in a Grothendieck group of Chow motives. They specialize to p-adic Igusa local zeta functions and to the topological zeta functions we introduced several years ago. We study their basic properties, such as functional equations, and their relation with motivic n

J. Denef, F. Loeser

We study the scheme of formal arcs on a singular algebraic variety and its images under truncations. We prove a rationality result for the Poincare series of these images which is an analogue of the rationality of the Poincare series associated to p-adic points on a p-adic variety. The main tools which are used are semi-algebraic geometry in spaces of power

Abdelghani Zeghib

Geometric problems are usually formulated by means of (exterior) differential systems. In this theory, one enriches the system by adding algebraic and differential constraints, and then looks for regular solutions. Here we adopt a dual approach, which consists to enrich a plane field, as this is often practised in control theory, by adding brackets of the ve

Andrei Okounkov

We classify all irreducible admissible representations of three Olshanski pairs connected to the infinite symmetric group. In particular, our methods yield two simple proofs of the classical Thoma's description of the characters of the infinite symmetric group. Also, we discuss a certain operation called mixture of representations which provides a unifor

C. G. Callan, L. Thorlacius

We analyze scattering of string modes at string junctions of type IIB string theory. In the infrared limit, certain orthogonal linear combinations of the fields on the different strings satisfy either Dirichlet or Neumann boundary conditions. We confirm that the worldsheet theory of a general string network has eight conserved supercharges in agreement with

George Zoupanos

N = 1, all-loop Finite Unified Theories (FUTs) are very interesting not only since they realize an old theoretical dream, but also due the remarkable predictive power of particular models as well as for providing candidates that might shed light in non-perturbative Physics. Here we discuss (a) the recent developments concerning the soft supersymmetry breakin

J. S. Dowker, Klaus Kirsten

We consider smeared zeta functions and heat-kernel coefficients on the bounded, generalized cone in arbitrary dimensions. The specific case of a ball is analysed in detail and used to restrict the form of the heat-kernel coefficients $A_n$ on smooth manifolds with boundary. Supplemented by conformal transformation techniques, it is used to provide an effecti

D. J. Broadhurst

In each of the 10 cases with propagators of unit or zero mass, the finite part of the scalar 3-loop tetrahedral vacuum diagram is reduced to 4-letter words in the 7-letter alphabet of the 1-forms $Ω:=dz/z$ and $ω_p:=dz/ (λ^{-p}-z)$, where $λ$ is the sixth root of unity. Three diagrams yield only $ζ(Ω^3ω_0)=1/90π^4$. In two cases $π^4$ combines with the Euler

Morten Krogh

We develop a matrix model for the SO(32) Heterotic string with certain Wilson lines on the lightlike circle. This is done by using appropriate T-dualities. The method works for an infinite number of Wilson lines, but not for all. The matrix model is the theory on the D-string of type I wrapped on a circle with a SO(32) Wilson line on the circle. The radius o

Amihay Hanany, Matthew J. Strassler, Angel M. Uranga

We show how to use D and NS fivebranes in Type IIB superstring theory to construct large classes of finite N=1 supersymmetric four dimensional field theories. In this construction, the beta functions of the theories are directly related to the bending of branes; in finite theories the branes are not bent, and vice versa. Many of these theories have multiple

Nima Arkani-Hamed, Savas Dimopoulos, Gia Dvali

We propose a new framework for solving the hierarchy problem which does not rely on either supersymmetry or technicolor. In this framework, the gravitational and gauge interactions become united at the weak scale, which we take as the only fundamental short distance scale in nature. The observed weakness of gravity on distances $\gsim$ 1 mm is due to the exi

M. Steinhauser

In this note the leptonic contribution to the running of the electromagnetic coupling constant is discussed up to the three-loop level. Special emphasize is put on the evaluation of the double-bubble diagrams.

John F. Donoghue, Barry R. Holstein

Baryon chiral perturbation theory as conventionally applied using dimensional regularization has a well-known problem with the convergence of the SU(3) chiral expansion. One can reformulate the theory equally rigorously using a momentum-space cutoff and we show that the convergence is thereby greatly improved for reasonable values of the cutoff. In effect, t

Christopher Kolda, Stefan Pokorski, Nir Polonsky

Within the context of supergravity-coupled supersymmetry, fields which are gauge and global singlets are usually considered anathema. Their vacuum expectation values are shifted by quadratically divergent tadpole diagrams which are cutoff at the Planck scale, destabilizing the classical potential and driving the singlet field to large values. We demonstrate

G. L. Fogli, E. Lisi, D. Montanino

The two possible Mikheyev-Smirnov-Wolfenstein (MSW) solutions of the solar neutrino problem (one at small and the other at large mixing angle), up to now tested mainly through absolute neutrino flux measurements, require flux-independent tests both for a decisive confirmation and for their discrimination. To this end, we perform a joint analysis of various f

John Ellis, Smaragda Lola, Graham G. Ross

We investigate the possibility of constructing models of R-violating LQD Yukawa couplings using a single U(1) flavour-symmetry group and supermultiplet charge assignments that are compatible with the known hierarchies of quark and lepton masses. The mismatch of mass and current eigenstates inferred from the known charged-current mixing induces the propagatio

A. Denner, S. Dittmaier, M. Roth

Numerical results on non-factorizable corrections to e+e- --> WW --> 4fermions with semi-leptonic and hadronic final states, as well as to e+e- --> ZZ --> 4fermions, are presented. The corrections turn out to be small in comparison to the experimental uncertainty of LEP2, but they might compete with the expected accuracy at future e+e--colliders.

G. Moortgat-Pick, H. Fraas, A. Bartl, W. Majerotto

We study the process e^+ e^- -> chi^0_1 chi^0_2 and the subsequent decay chi^0_2 -> chi^0_1 l^{+} l^{-}$ with polarized beams, including the complete spin correlations of chi^0_2$. We present numerical results for the lepton energy and angular distributions, and for the distribution of the opening angle between the leptons for sqrt{s}=500 GeV. The effects of

Warren B. Perkins, Anne-Christine Davis

A class of grand unified theories with symmetry breaking scale of order $10^{16} GeV$ have a Higgs particle with mass in the $TeV$ scale. The cosmology of such theories is very different from usual. We study the cosmic strings obtained in such theories. These strings are much fatter than usual and their mass per unit length is reduced, resulting in a signifi

K. K. Sharma, R. C. Verma

We investigate two-body Cabibbo-angle enhanced weak decays of charmed baryons into octet baryon and pseudoscalar meson in the current algebra framework with inclusion of the factorization terms which are evaluated using the HQET guided baryonic form factors. We obtain the branching ratios and asymmetry parameters for various Cabibbo-enhanced decays of $Λ_c^+

Benoit Vanderheyden, Gordon Baym

We generalize the concept of conserving, Phi-derivable, approximations to relativistic field theories. Treating the interaction field as a dynamical degree of freedom, we derive the thermodynamic potential in terms of fully dressed propagators, an approach which allows us to resolve the entropy of a relativistic plasma into contributions from its interacting

B. Abbott

We report on a search for charge 1/3 third generation leptoquarks (LQ) produced in pbarp collisions at sqrt(s) = 1.8 TeV using the D0 detector at Fermilab. Third generation leptoquarks are assumed to be produced in pairs and to decay to a tau neutrino and a b quark with branching fraction B. We place upper limits on sigma(pbarp to LQbarLQ)xB^2 as a function

M. N. Achasov, A. V. Berdyugin, A. V. Bozhenok, D. A. Bukin

Upper bound 6*10^{-4} with 90% confidence is reported for the eta -> pi^0 pi^0 decay from the SND experiment at the VEPP-2M collider.

E. N. Glass, J. P. Krisch

We extend the Vaidya radiating metric to include both a radiation field and a string fluid. Assuming diffusive transport for the string fluid, we find new analytic solutions of Einstein's field equations. Our new solutions represent an extention of Xanthopoulos superposition.

José A. C. Nogales, Anzhong Wang

The stability of the cosmological event horizons (CEHs) of a class of non-static global cosmic strings is studied against perturbations of gravitational waves and massless scalar field. It is found that the perturbations of gravitational waves always turn the CEHs into non-scalar weak spacetime curvature singularities, while the ones of massless scalar field

S. R. Brandt, K. Camarda, E. Seidel

We present a new class of 3D black hole initial data sets for numerical relativity. These data sets go beyond the axisymmetric, ``gravity wave plus rotating black hole'' single black hole data sets by creating a dynamic, distorted hole with adjustable distortion parameters in 3D. These data sets extend our existing test beds for 3D numerical relativi

W. O. Putikka, M. U. Luchini, R. R. P. Singh

We have calculated the high temperature series for the momentum distribution function n_k of the 2D t-J model to 12th order in inverse temperature. By extrapolating the series to T=0.2J we investigate the possibility of hole pockets in the t-J model. We find no indication of hole pockets at an electron density of n=0.9 with J/t=0.5 or J/t=1.0.

W. O. Putikka, M. U. Luchini, R. R. P. Singh

We have calculated the high temperature series for the momentum distribution function n_k of the 2D t-J model to 12th order in inverse temperature. By extrapolating the series to T=0.2J we searched for a Fermi surface of the 2D t-J model. We find that three criteria used for estimating the location of a Fermi surface violate Luttinger's Theorem, implying

Z. Yusof, L. Coffey

The asymmetry in the conductance peaks shown in recent PCT and STM measurements may be a signature of the d-wave gap. This is based on our model for the tunneling density of states (DOS) which incorporates the group velocity, tunneling directionality, and a realistic band structure. We also make the comparison with the isotropic s-wave and extended s-wave ga

K. Maiti, Priya Mahadevan, D. D. Sarma

We study the evolution of the spectral function with progressive hole doping in a Mott insulator, $La_{1-x}Ca_xVO_3$ with $x$ = 0.0 - 0.5. The spectral features indicate a bulk-to-surface metal-insulator transition in this system. Doping dependent changes in the bulk electronic structure are shown to be incompatible with existing theoretical predictions. An

Andres Jerez, Natan Andrei, Gergely Zarand

A complete Bethe Ansatz solution of the SU(N)xSU(f) Coqblin Schrieffer model and a detailed analysis of some physical applications of the model are given. As in the usual multichannel Kondo model a variety of Fermi liquid and non-Fermi liquid (NFL) fixed points is found, whose nature depends on the impurity representation, $μ$. For $μ=f$ we find a Fermi liqu

Matteo Campellone, Silvio Franz, Giorgio Parisi

In this note we formulate a finite dimensional generalization of the Random Energy Model (REM) where we introduce a geometry and spatial correlations between energies. We study the model in dimension one by transfer matrix techniques and we look at the crossover from one dimensional to mean-field behaviour. In a first version of the model the mean field limi

G. Haran, P. J. Hirschfeld, M. Sigrist

We discuss the weak-coupling BCS theory of the heavy fermion superconductor UPt_3, accounting for that system's anisotropic, multisheeted Fermi surface by expanding the order parameter and pair potential in terms of appropriate basis functions of the irreducible representations of the D_6h crystal point group. Within a phenomenological model for the elec

Natan Andrei, Michael R. Douglas, Andres Jerez

We identify a non Fermi Liquid (NFL) class of fixed points describing the infrared behaviour of interacting chiral fermions in one dimension. The thermodynamic properties and asymptotic correlation functions are characterized by universal exponents, which we determine by means of conformal and Bethe-Ansatz techniques. The mechanism leading to the breakdown o

T. Brandes, J. Inoue, A. Shimizu

We investigate a superradiating system coupled to external reservoirs. Under conditions where electrons tunneling at a rate $T$ act like an electron pump, we predict a novel phenomenon in the form of oscillations with a frequency $ω\simeq \sqrt{2ΓT}$ that appear in the (photon) emission intensity, where $Γ$ is the spontaneous decay rate of a single two-level

R. Schiller, W. Mueller, W. Nolting

The electronic quasiparticle structure of a ferromagnetic local moment film is investigated within the framework of the s-f model. For the special case of a single electron in an otherwise empty energy band being exchange coupled to a fully ordered localised spin system the problem can be solved exactly and, for the spin-down electron, some marked correlatio

Reinhold Egger, Alexander O. Gogolin

We derive the effective low-energy theory for single-wall carbon nanotubes including the Coulomb interactions among electrons. The generic model found here consists of two spin-1/2 fermion chains which are coupled by the interaction. We analyze the theory using bosonization, renormalization-group techniques, and Majorana refermionization. Several experimenta

Xi Dai, Zhao-Bin Su

In the context of t-J model we show that in underdoped regime,beside the usual long wave length gauge field fluctuation, an additional low energy fluctuation, staggered gauge field fluctuation plays a crucial role in the evolution of Fermi surface(FS) as well as the line shape of spectral function for the cuprates. By including the staggered gauge field fluc

Victor S. L'vov, Itamar Procaccia, Damien Vandembroucq

In a series of recent works it was proposed that shell models of turbulence exhibit inertial range scaling exponents that depend on the nature of the dissipative mechanism. If true, and if one could imply a similar phenomenon to Navier-Stokes turbulence, this finding would cast strong doubts on the universality of scaling in turbulence. In this Letter we pro

Shunichi Tsuge

A unique form of turbulent-transport equations is derived based on first principles.The role of nonequilibrium statistical mechanics employed to describe the phenomenology is that it enables to single out the unique form consistent with master equation of Liouville, a prerequisite not met with existing equations for turbulence modeling.The equation is variab

Shunichi Tsuge

An open question of whether phenomenological fluid equations to be used for direct numerical simulation of turbulence are warranted on `first principles' is addressed, and the problem is posed using Klimontovich microscopic density to replace the Boltzmann function of the classical statistical mechanics. For inert monatomic gases, it is shown that all th

D. Queloz, S . Allain, J. -C. Mermilliod, J. Bouvier

We present new vsini measurements for 235 low-mass stars in the Pleiades. The differential rotational broadening has been resolved for all the stars in our sample. These results, combined with previously published measurements, provide a complete and unbiased rotation data set for stars in the mass range from 0.6 to 1.2 Msol. Applying a numerical inversion t

Arjun Dey, Hyron Spinrad, Daniel Stern, James R. Graham

We report the discovery of Lyman alpha emission from a galaxy at z=5.34, the first object at z>5 with a spectroscopically confirmed redshift. The faint continuum emission (m(8000A)=27 AB mag), relatively small rest-frame equivalent width of the emission line (rest equivalent width of 95A), and limits on the NV/Lya ratio suggest that this is a star-forming ga

H. J. Haubold

Wavelet analysis offers an alternative to Fourier based time-series analysis and is particularly useful when spectral features are time dependent. We analyze the solar neutrino capture rate of the radiochemical Homestake chlorine experiment with abbreviated Morlet wavelets, using Foster's (AJ, 111, 1709 (1996)) rescaled wavelet technique. We emphasize th

Philip D. Mannheim

Some recent supernovae studies have extended the distance versus velocity Hubble plot to very high redshift, and have revealed the apparent presence of a cosmic repulsion. We show that such a repulsion has a natural origin within conformal gravity, a fully covariant candidate alternative to standard gravity, and that it arises from the gravitational field it

I. Saviane, G. Piotto, F. Fagotto, S. Zaggia

We have completely mapped the globular cluster NGC 1851 with VI CCD photometry, obtaining a CMD for ca. 20500 stars. From the apparent luminosity of the HB we derive a distance modulus (m-M)o=15.44+/-0.20. The presence of 7 "supra-HB" stars is confirmed. Six of them are identified as evolved descendants from HB progenitors. Synthetic HR diagrams demo

F. R. Pearce

I investigate the process of converting gas into stars within the framework of a standard cosmological model. By examining the set of objects grown in a combined N-body plus smoothed particle hydrodynamics simulation with those obtained in similar models where some of the cold, dense gas was replaced by collisionless ``star'' particles I show that it

Inger Jorgensen, Helge Jonch-Sorensen

We have studied the poor southern cluster of galaxies S639. Based on new Stromgren photometry of stars in the direction of the cluster we confirm that the galactic extinction affecting the cluster is large. We find the extinction in Johnson B to be A_B = 0.75+-0.03. We have obtained new photometry in Gunn r for E and S0 galaxies in the cluster. If the Fundam

T. M. Brown, J. Christensen-Dalsgaard

The Solar Diameter Monitor measured the duration of solar meridian transits during the 6 years 1981 to 1987, spanning the declining half of solar cycle 21. We have combined these photoelectric measurements with models of the solar limb-darkening function, deriving a mean value for the solar near-equatorial radius of 695.508 +- .026 Mm. Annual averages of the

P. N. Best, C. Carilli, S. T. Garrington, M. S. Longair

High resolution, deep radio images are presented for two distant radio galaxies, 3C324 (z=1.206) and 3C368 (z=1.132), which are both prime examples of the radio-optical alignment effect seen in powerful radio galaxies with redshifts z > 0.6. Radio observations were made using the Very Large Array in A-array configuration at 5 and 8 GHz, and using the MERLIN

P. Giommi et al

A long ($>100,000$ seconds) observation of the bright BL Lac object PKS 2155-304 has been carried out with the Narrow Field Instruments of the BeppoSAX satellite as part of the Science Verification Phase. The source was detected between 0.1 and about 100 keV at an intermediate intensity level compared to previous observations. The unique spectral coverage of

Deepak Jain, N. Panchapakesan, S. Mahajan, V. B. Bhatia

We study the effect of the cosmological constant on the statistical properties of gravitational lenses in flat cosmologies (Omega_{0}+lambda_{0} = 1). It is shown that some of the lens observables are strongly affected by the cosmological constant, especially in a low--density universe, and its existence might be inferred by a statistical study of the lenses

M. van Noort, T. Lanz, H. J. G. L. M. Lamers, R. L. Kurucz

We present high-quality HST/GHRS spectra in the Hydrogen L alpha spectral region of Vega and Sirius-A. Thanks to the signal-to-noise ratio achieved in these observations and to the similarity of the two spectra, we found clear evidence of emission features in the low flux region, 1190-1222 A. These emission lines can be attributed unambiguously to Fe II and

F. Matteucci, R. Ponzone, B. K. Gibson

We revisit the problem of the flat slope of the Mg2 versus <Fe> relationship found for nuclei of elliptical galaxies (Faber et al. 1992; Worthey et al. 1992; Carollo et al. 1993; Davies et al. 1993), indicating that the Mg/Fe ratio should increase with galactic luminosity and mass. We transform the abundance of Fe, as predicted by classic wind models and alt

Graeme H. Smith, Christopher W. Churchill

Echelle spectra have been obtained of the Ca II H and K lines for a sample of metal-poor subdwarf stars as well as for a number of nearby Population I dwarfs selected from among those included in the Mount Wilson HK survey. The main conclusion of this paper is that Ca II H- and K-line emission does occur among subdwarfs. It is particularly notable among thos

M. A. Malkan, V. Gorjian, R. Tam

We obtained 500-second F606W WFPC2 images of 256 of the nearest (z<0.035) Seyfert 1,Seyfert 2, and starburst galaxies. Less than 10% show tidal features or multiple nuclei. The incidence of inner starburst rings is about 10% in both classes of Sy galaxies. In contrast, galaxies with H II region emission line spectra appear substantially more irregular becaus

B. L. Altshuler, M. E. Gershenson, I. L. Aleiner

Conduction electrons in disordered metals and heavily doped semiconductors at low temperatures preserve their phase coherence for a long time: phase relaxation time $τ_ϕ$ can be orders of magnitude longer than the momentum relaxation time. The large difference in these time scales gives rise to well known effects of weak localization, such as anomalous magne

Gary T. Horowitz, Simon F. Ross

We point out that the recent conjecture relating large N gauge theories to string theory in anti-de Sitter spaces offers a resolution in principle of many problems in black hole physics. This is because the gauge theory also describes spacetimes which are not anti-de Sitter, and include black hole horizons and curvature singularities.

Alexander Vilenkin

Singular instantons of the type introduced by Hawking and Turok (hep-th/9802030) lead to unacceptable physical consequences and cannot, therefore, be used to describe the creation of open universes.

C. N. A. Willmer, L. Nicolaci da Costa, P. S. Pellegrini

We use the two-point correlation function to calculate the clustering properties of the recently completed SSRS2 survey. The redshift space correlation function for the magnitude-limited SSRS2 is given by xi(s)=(s/5.85 h-1 Mpc)^{-1.60} for separations between 2 < s < 11 h-1 Mpc, while our best estimate for the real space correlation function is xi(r) = (r/5.

Shirish M. Chitanvis

Paper has been withdrawn for major repairs.

Cristian F. Moukarzel

In this letter, structural rigidity concepts are used to understand the origin of instabilities in granular aggregates. It is shown that: a) The contact network of a noncohesive granular aggregate becomes exactly isostatic in the limit of large stiffness-to-load ratio. b) Isostaticity is responsible for the anomalously large susceptibility to perturbation of

Hans-Juergen Borchers, Detlev Buchholz

Starting from the assumption that vacuum states in de Sitter space look for any geodesic observer like equilibrium states with some a priori arbitrary temperature, an analysis of their global properties is carried out in the algebraic framework of local quantum physics. It is shown that these states have the Reeh-Schlieder property and that any primary vacuu

A. P. Bakulev, S. V. Mikhailov

We apply the nonlocal condensate formalism to construct generalized sum rules (including $O(\as)$-radiative corrections) for $π$-, $ρ$- and $ρ&#39;$-meson wave functions of twist 2. Besides, we predict the lepton decay constant $f_{ρ&#39;}$ and estimate the mass of $ρ&#39;$-meson. For all these mesons we obtain the first 10 moments of longitudinal wave funct

K. Pinn

A number of observations are made on Hofstadter&#39;s integer sequence defined by Q(n)= Q(n-Q(n-1))+Q(n-Q(n-2)), for n > 2, and Q(1)=Q(2)=1. On short scales the sequence looks chaotic. It turns out, however, that the Q(n) can be grouped into a sequence of generations. The k-th generation has 2**k members which have ``parents&#39;&#39; mostly in generation k-

Silvio Franz, Marc Mézard, Giorgio Parisi, Luca Peliti

We corroborate the idea of a close connection between replica symmetry breaking and aging in the linear response function for a large class of finite-dimensional systems with short-range interactions. In these system, characterized by a continuity condition with respect to weak random perturbations of the Hamiltonian, the ``fluctuation dissipation ratio&#39;

Mikhail Z. Iofa, Leopoldo A. Pando Zayas

Four-dimensional magnetic black holes including dilaton and abelian gauge fields which are solutions of supergravity can also be obtained by dimensional reduction of the Einstein-Maxwell gravity in five dimensions. In the extremal case the five-dimensional solutions have horizon and their near-horizon geometry is $AdS_3\times S^2 $. In the non-extremal case

Toshiyuki Kanazawa, M. Kawasaki, Naoshi Sugiyama, T. Yanagida

The M-theory, the strong-coupling heterotic string theory, presents various interesting new phenomenologies. The M-theory bulk axion is one of these. The decay constant in this context is estimated as $F_a\simeq 10^{16}$ GeV. Direct searches for the M-theory axion seem impossible because of the large decay constant. However, we point out that large isocurvat

Won Tae Kim, Myung Seok Yoon

We consider two-dimensional Brans-Dicke theory to study the initial singularity problem. It turns out that the initial curvature singularity can be finite for a certain Brans-Dicke constant $ω$ by considering the quantum back reaction of the geometry. For $ω=1$, the universe starts with the finite curvature scalar and evolves into the flat spacetime. Further

H. W. Lee, N. J. Kim, Y. S. Myung

We study the dynamical behavior of the BTZ (Banados-Teitelboim-Zanelli) black hole with the low-energy string effective action. The perturbation analysis around the BTZ black hole reveals a mixing between the dilaton and other fields. Introducing the new gauge (dilaton gauge), we disentangle this mixing completely and obtain one decoupled dilaton equation. W

Taksu Cheon

We analyze the eigenvalue problem of a quantum particle on the line with the generalized pointlike potential of three parameter family. It is shown that the energy surface in the parameter space has a set of singularities, around which different eigenstates are connected in the form of paired spiral stairway. An examplar wave-function aholonomy is displayed

Asantha R. Cooray

Under the assumption that the gas mass fraction of galaxy clusters estimated out to an outer hydrostatic radius is constant, it is possible to constrain the cosmological parameters by using the angular diameter distance relation with redshift. We applied this to a sample of galaxy clusters from redshifts of 0.1 to 0.94, for which published gas and total mass

E. Abdalla, R. Banerjee

We reconsider the problem of quantising a particle on the $D$-dimensional sphere. Adopting a Lagrangian method of reducing the degrees of freedom, the quantum Hamiltonian is found to be the usual Schrödinger operator without any boundary term. The equivalence with the Dirac Hamiltonian approach is demonstrated, either in the cartesian or in the curvilinear b

Joseph E. Avron, Ruedi Seiler, Barry Simon

We study the relative index of two orthogonal infinite dimensional projections which, in the finite dimensional case, is the difference in their dimensions. We relate the relative index to the Fredholm index of appropriate operators, discuss its basic properties, and obtain various formulas for it. We apply the relative index to counting the change in the nu

Alan R Champneys, Boris A Malomed, Mark J friedman

The effect of dispersion or diffraction on zero-velocity solitons is studied for the generalized massive Thirring model describing a nonlinear optical fiber with grating or parallel-coupled planar waveguides with misaligned axes. The Thirring solitons existing at zero dispersion/diffraction are shown numerically to be separated by a finite gap from three iso

Harel Primack, Reinhold Blümel

Small ion crystals in a Paul trap are stable even in the absence of laser cooling. Based on this theoretically and experimentally well-established fact we propose the following diagnostic criterion for establishing the presence of a crystallized beam: Absence of heating following the shut-down of all cooling devices. The validity of the criterion is checked

Stefan Goedecker, Oleg Ivanov

Wavelets are a powerful new mathematical tool which offers the possibility to treat in a natural way quantities characterized by several length scales. In this article we will show how wavelets can be used to solve partial differential equations which exhibit widely varying length scales and which are therefore hardly accessible by other numerical methods. A