September 1999 arXiv papers — page 13

A. J. Sargeant, M. S. Hussein, M. P. Pato, M. Ueda

The strength function of a single state $|d>$ is studied using the deformed Gaussian orthogonal ensemble. In particular we study the dependence of the spreading width of $|d>$ on the degree of mixing.

D. Davesne, Y. J. Zhang, G. Chanfray

We discuss medium modifications of the unitarized pion-pion interaction in the nuclear medium. We incorporate both the effects of chiral symmetry restoration and the influence of collective nuclear pionic modes originating from the p-wave coupling of the pion to delta-hole configurations. We show in particular that the dropping of the sigma meson mass signif

K. B. Korotchenko

In this paper formulate the hypothesis that in a molecule $D_2 O$ (in a cluster of heavy water $(D_2 O)_N)$ when its specific energy is of the order of 150 eV one of the molecular bonds $O - D$ is changed into $O - D_μ$ i.e. a molecule $D_2 O$ transforms into a muonic molecule. This postulate is necessary to explain the experiment which was carried out in Br

Jean-Marc Richard

We review ideas and speculations concerning possible bound states or resonances coupled to the nucleon-antinucleon channel.

SAMPLE collaboration, D. T. Spayde

We report a new measurement of the parity-violating asymmetry in elastic electron scattering from the proton at backward scattering angles. This asymmetry is sensitive to the strange magnetic form factor of the proton as well as electroweak axial radiative corrections. The new measurement of A=-4.92 +- 0.61 +- 0.73 ppm provides a significant constraint on th

R. Nouicer, C. Beck, S. J. Sanders, A. Szanto de Toledo

Fragment-fragment-$γ$ coincidences have been measured for $\rm ^{28}Si + {^{28}Si}$ at an energy corresponding to the population of a conjectured resonance in $^{56}$Ni. Fragment angular distributions as well as $γ$-ray angular correlations indicate that the spin orientations of the outgoing fragments are perpendicular to the orbital angular momentum. This d

M. Rousseau, C. Beck, C. Bhattacharya, V. Rauch

Inclusive as well as exclusive energy spectra of the light charged particles emitted in the $^{28}$Si ($E_{lab}$=112.6 MeV) + $^{12}$C reaction has been measured using the {\bf ICARE} multidetector array. The data have been analysed by statistical-model calculations using a spin-dependent level density parametrization. The results suggest significant deforma

Elliott Lieb, Michael Loss

Various models of charged particles interacting with a quantized, ultraviolet cutoff radiation field (but not with each other) are investigated. Upper and lower bounds are found for the self- or ground state-energies without mass renormalization. For $N$ fermions the bounds are proportional to $N$, but for bosons they are sublinear, which implies `binding&#3

Anders S. Buch

In our joint paper with W. Fulton (math.AG/9804041) we prove a formula for the cohomology class of a quiver variety. This formula involves a new class of generalized Littlewood-Richardson coefficients, all of which surprisingly seem to be non-negative. We conjecture that each of these coefficients count the number of sequences of semistandard Young tableaux

J. Franecki, M. Kapranov

For an irreducible subvariety Z in an algebraic group G we define a nonnegative integer gdeg(Z) as the degree, in a certain sense, of the Gauss map of Z. It can be regarded as a substitution for the intersection index of the conormal bundle to Z with the zero section of T^*G, even though G may be non-compact. For G a semiabelian variety (in particular, an al

Moti Gitik, Saharon Shelah

We show that some cardinal arithmetic configurations related to the negation of the Shelah Weak Hypothesis and natural from the forcing point of view are impossible.

Sung Ho Wang

The conservation laws of the third order quasilinear scalar evolution equations are considered via differential system and characteristic cohomology. We find a subspace of 2 forms in the infinite prolonged space in which every conservation law has a unique representative. The structure of this subspace naturally gives rise to the convenient notion of the wei

Andrei Tyurin

This paper combines algebraic and Lagrangian geometry to construct a special basis in every space of conformal blocks, the Bohr-Sommerfeld (BS) basis. We use the method of [D. Borthwick, T. Paul and A. Uribe, Legendrian distributions with applications to the non-vanishing of Poincaré series of large weight, Invent. math, 122 (1995), 359-402, preprint hep-th/

Piero de Mottoni, Michelle Schatzman

It is possible to choose the parameters of a real quintic Ginzburg-Landau equation so that it possesses localized pulse-like solutions; Thual and Fauve have observed numerically that these pulses are stabilized by perturbations destroying the gradient structure of the real equation. For parameters such that the real part of the equations possesses pulses wit

Alexander G. Elashvili, Dmitri I. Panyushev

We give a classification of the principal and distinguished nilpotent pairs in all classical Lie algebras. As a classification of the principal pairs in the exceptional simple Lie algebras was obtained earlier (see Appendix to Ginzburg's preprint math.AG/9903059), we thus have a complete classification of principal nilpotent pairs.

A. Coste, T. Gannon

We address here the question of whether the characters of an RCFT are modular functions for some level N, i.e. whether the representation of the modular group SL_2(Z) coming from any RCFT is trivial on some congruence subgroup. We prove that if the matrix T, associated to $(\matrix{1&1\cr 0&1})\in{\rm SL}_2(\Z)$, has ODD order, then this must be so. When the

Wilberd van der Kallen

We prove that in positive characteristic a module with good filtration for a group of type E6 restricts to a module with good filtration for a subgroup of type F4. (Recall that a filtration of a module for a semisimple algebraic group is called good if its layers are dual Weyl modules.) Our result confirms a conjecture of Brundan for one more case. The metho

Alberto Garcia

It is shown that the charged non-diagonal BTZ (2+1)-spacetime is not a solution of the Einstein-Maxwell field equations with cosmological constant.

Jae-weon Lee, Seoktae Koh, Chanyong Park, Sang Jin Sin

The oscillating inflation model recently proposed by Damour and Mukhanov is investigated with a non-minimal coupling. Numerical study confirms an inflationary behavior and the density perturbation is obtained. A successful inflation requires the gravity-dilaton coupling to be small.

Bjorn Andreas, Gottfried Curio

We give an indirect argument for the matching $G^2=-π_* γ^2$ of four-flux and discrete twist in the duality between N=1 heterotic string and $F$-theory. This treats in detail the Euler number computation for the physically relevant case of a Calabi-Yau fourfold with singularities.

Sven Bergmann, Yosef Nir

The most sensitive experimental searches for $D-\bar D$ mixing use $D^0 \to K^+ π^-$ decays. It is often assumed that effects of New Physics and, in particular, CP violation, can appear through the mixing, while the $c \to d u \bar s$ decay amplitude cannot have significant contributions from New Physics and is, therefore, CP conserving to a good approximati

Sven Bergmann, Yuval Grossman, Damien M. Pierce

We investigate whether flavor changing neutrino interactions (FCNIs) can be sufficiently large to provide a viable solution to the atmospheric neutrino problem. Effective operators induced by heavy boson exchange that allow for flavor changing neutrino scattering off quarks or electrons are related by an $SU(2)_L$ rotation to operators that induce anomalous

A. H. Mueller

A Boltzmann equation is given for the early stages of evolution of the gluon system produced in a head-on collision. The collision term is taken from gluon- gluon approximation. < p_\perp > and < p_z^2 > are evaluated as a function of time using initial conditions taken from the McLerran-Venugopalan model.

A. J. Buchmann

Information on the intrinsic deformation of the proton can be obtained by studying the electromagnetic p-->Delta+ quadrupole transition. Recent experiments have shown that the electric quadrupole (E2) strength in gamma p --> Delta+ is about 10 times larger than predicted by the simple quark model using only one-body currents. Our analysis provides evidence f

Matthew Wingate

The strange quark mass has been computed using a lattice action which possesses continuum--like chiral symmetry to good precision, namely the domain wall fermion action. This talk surveys this action and the recent calculation of m_s by the RIKEN/BNL/CU collaboration. This result is put into context by briefly summarizing other recent lattice studies.

A. Hebecker, E. Meggiolaro, O. Nachtmann

The small-x_Bj limit of deep inelastic scattering is related to the high-energy limit of the forward Compton amplitude in a familiar way. We show that the analytic continuation of this amplitude in the energy variable is calculable from a matrix element in Euclidean field theory. This matrix element can be written as a Euclidean functional integral in an eff

M. Rybczynski, G. Wilk, Z. Wlodarczyk, M. Biyajima

We demonstrate on simple examples that oscillatory behaviour of moments of multiplicity distributions P(n) observed in e^+e^- annihilations, in hadronic pp collisions and in collisions on nuclei, p+A, is to a large extend caused by the experimental artifact of measuring only limited range of P(n). In particular we show that by applying a suitable universal c

K. Gallmeister, B. Kämpfer, O. P. Pavlenko

An analysis of the dilepton measurements of the reactions Pb(158 A$\cdot$GeV) + Au, Pb by the CERES and NA50 collaborations points to a unique thermal source contributing to the invariant mass and transverse momentum spectra.

H. Eberl, S. Kraml, W. Majerotto, A. Bartl

We present a phenomenological analysis of production and decays of stops, sbottoms, and staus in e+e- collisions with sqrt(s) = 500 - 800 GeV. We include SUSY-QCD and Yukawa coupling corrections as well as initial state radiation. We show that e- beam polarization is a powerful tool for a determination of the underlying SUSY parameters. Using in addition a p

Marc Chemtob, Grégory Moreau

We examine the contributions from the R-parity odd interactions, $ ł_{ijk} L_iL_jE_k^c $ and $ ł&#39;_{ijk} L_i Q_j D^c_k$, to the total rates and the CP asymmetry rates in the production of fermion-antifermion (lepton, down and up quark) pairs and slepton-antislepton pairs of different flavors at leptonic colliders. For the top-charm associated production c

Tianjun Li

In the simplest compactification, we discuss the intermediate unification in M-theory on $S^1/Z_2$, and point out that we can push the eleven dimension Planck scale to the TeV range if the gauge coupling in the hidden sector is super weak, and the particles in the hidden sector might become candidates of dark matter. We also discuss the soft terms in non-sta

A. Duncan, E. Eichten, H. Thacker

A truncated determinant algorithm is used to study the physical effects of the quark eigenmodes associated with eigenvalues below 400 MeV. This initial study focuses on coarse lattices (with O(a^2) improved gauge action), light internal quark masses and large physical volumes. Four bellwether full QCD processes are discussed: topological charge distributions

P. Emirdag, R. Easther, G. S. Guralnik, S. C. Hahn

The Source Galerkin Method is a new numerical technique that is being developed to solve Quantum Field Theories on the continuum. It is not based on Monte Carlo techniques and has a measure to evaluate relative errors. It promises to increase the accuracy and speed of calculations, and takes full advantage of symmetries of the theory. The application of this

MILC Collaboration, Claude Bernard, Thomas DeGrand, Carleton DeTar

We describe a calculation of heavy-light decay constants including virtual quark loop effects. We have generated dynamical gauge configurations at three $β$ values using two flavors of Kogut-Susskind quarks with a range of masses. These are analyzed with a Wilson valence quark action. Preliminary results based on a ``fat-link&#39;&#39; clover valence quark a

R. Aloisio, V. Azcoiti, G. Di Carlo, A. Galante

The analytical results obtained in the infinite mass and strong coupling limits of QCD are difficult to reconcile with the predictions of the Monomer Dimer Polymer algorithm. We have reconsidered in detail the results obtained with this simulation scheme and evidences of severe convergence problems are presented for the SU(3) and SU(2) gauge group.

J. Cox, C. Gattringer, K. Holland, B. Scarlet

Numerical simulations of numerous quantum systems suffer from the notorious sign problem. Important examples include QCD and other field theories at non-zero chemical potential, at non-zero vacuum angle, or with an odd number of flavors, as well as the Hubbard model for high-temperature superconductivity and quantum antiferromagnets in an external magnetic f

H1 Collaboration, C. Adloff

The first observation of open b production in ep collisions is reported. An event sample containing muons and jets has been selected which is enriched in semileptonic b quark decays. The visible cross section σ(ep -> b \bar{b}X -> μX&#39;) for Q^2 < 1 GeV^2, 0.1 < y < 0.8 is measured to be 0.176+-0.016(stat.)+0.026-0.017(syst.) nb for the muons to be detecte

Roberto Scipioni

This is a first paper of a series in which we give some generalizations of the Obukhov theorem in the Tucker-Wang approach to Metric- Affine gravity in which we consider more general actions containing scalar and in general fields which do not depend on the metric or connection.

F. J. Chinea, M. J. Pareja

Geometric features (including convexity properties) of an exact interior gravitational field due to a self-gravitating axisymmetric body of perfect fluid in stationary, rigid rotation are studied. In spite of the seemingly non-Newtonian features of the bounding surface for some rotation rates, we show, by means of a detailed analysis of the three-dimensional

V. A. Savchenko, T. P. Shestakova, G. M. Vereshkov

A way of constructing mathematically correct quantum geometrodynamics of a closed universe is presented. The resulting theory appears to be gauge-noninvariant and thus consistent with the observation conditions of a closed universe, by that being considerably distinguished from the conventional Wheeler - DeWitt one. For the Bianchi-IX cosmological model it i

B. Modak, S. Kamilya, S. Biswas

We present the gravitational coupling function $ω(ϕ)$ in the vacuum scalar-tensor theory as allowed by the Noether symmetry. We also obtain some exact cosmological solutions in the spatially homogeneous and isotropic background thereby showing that the attractor mechanism is not effective enough to reduce the theory to Einstein theory. It is observed that, a

Tekin Dereli, Yuri N. Obukhov

The low-energy (bosonic &#34;heterotic&#34;) string theory is interpreted as a universal limit of the Kaluza-Klein reduction when the dimension of an internal space goes to infinity. We show that such an approach is helpful in obtaining classical solutions of the string model. As a particular application, we obtain new exact static solutions for the two-dime

Bernd A. Berg

Monte Carlo simulation with {\it a-priori} unknown weights have attracted recent attention and progress has been made in understanding (i) the technical feasibility of such simulations and (ii) classes of systems for which such simulations lead to major improvements over conventional Monte Carlo simulations. After briefly sketching the history of multicanoni

Cristopher Moore, Jonathan Machta

The computational complexity of internal diffusion-limited aggregation (DLA) is examined from both a theoretical and a practical point of view. We show that for two or more dimensions, the problem of predicting the cluster from a given set of paths is complete for the complexity class CC, the subset of P characterized by circuits composed of comparator gates

J. Fernandez-Rossier, C. Tejedor, R. Merlin

We discuss light-heavy hole beats observed in transient optical experiments in GaAs quantum wells in terms of a free-boson coherent state model. This approach is compared with descriptions based on few-level representations. Results lead to an interpretation of the beats as due to classical electromagnetic interference. The boson picture correctly describes

M. P. Lilly, J. P. Eisenstein, L. N. Pfeiffer, K. W. West

Coulomb drag between two parallel two dimensional electron gases has been measured at high magnetic fields in samples with two different layer spacings. As the layer filling factor deviates from nu=1/2, we find that the magnitude of the drag is enhanced quadratically with Delta nu = nu - 1/2, and the curvature of the enhancement is insensitive to both the si

Anders W. Sandvik

The two-dimensional antiferromagnetic S=1/2 Heisenberg model with random bond dilution is studied using quantum Monte Carlo simulation at the percolation threshold (50% of the bonds removed). Finite-size scaling of the staggered structure factor averaged over the largest connected clusters of sites on L*L lattices shows that long-range order exists within th

J. -E. Wegrowe, A. Comment, Y. Jaccard, J. -Ph. Ansermet

Magnetoresistance measurements in the CPP geometry have been performed on single electrodeposited Co nanowires exchange biased on one side by a sputtered amorphous GdCo layer. This geometry allows the stabilization of a single domain wall in the Co wire, the thickness of which can be controlled by an external magnetic field. Comparing magnetization, resistiv

Barak Galanti, Zeev Olami

We discuss vibrational localization problems in glasses and disordered media in this paper. It is claimed that the essence of the localization problem is already observed in disordered lattice models. These kinds of vibrations belong to a different universality class than bonded electrons. Specifically, The eigenvectors are extended even in two dimensions. M

F. X. Magdaleno, J. Casademunt

We find that solvability theory selects a set of stationary solutions of the Saffman-Taylor problem with coexistence of two \it unequal \rm fingers advancing with the same velocity but with different relative widths $λ_1$ and $λ_2$ and different tip positions. For vanishingly small dimensionless surface tension $d_0$, an infinite discrete set of values of th

B. Valenzuela, M. A. H. Vozmediano, F. Guinea

The magnetic properties of the t-t&#39; Hubbard Model in the two dimensional square lattice are studied within an unrestricted Hartree-Fock approximation in real space. The interplay between antiferromagnetism, ferromagnetism, phase separation and inhomogeneous magnetic textures is studied. It is shown that, at sufficiently large values of t&#39;/t, a rich f

O. G. Balev, Nelson Studart

A microscopic treatment of edge magnetoplasmons (EMPs) is presented for the case of not-too-low temperatures in which the inequality $k_{B}T\gg \hbar v_{g}/\ell_{0}$, where $v_{g}$ is the group velocity of the edge states and $\ell_{0}$ is the magnetic length, is fulfilled, and for filling factors $ν=1(2)$. We have obtained independent EMP modes spatially sy

M. G. Noro, N. Kern, D. Frenkel

The phase behavior of colloid-polymer mixtures, and of solutions of globular proteins, is often interpreted in terms of a simple model of hard spheres with short-ranged attraction. While such a model yields a qualitative understanding of the generic phase diagrams of both colloids and proteins, it fails to capture one important difference: the model predicts

V. B. Eltsov, M. Krusius

Defects in the multi-dimensional macroscopic quantum field of the He-3 superfluids are localized objects with a topological charge and are topologically stable. They include point-like objects, vortex lines, planar domain-wall-like structures, and 3-dimensional textures, which may or may not include singular points or lines. An inventory of illustrations is

C. M. Canali

We have investigated numerically the electron addition spectra in quantum dots containing a small number (N < 11) of interacting electrons, in presence of strong disorder. For a short-range Coulomb repulsion, we find regimes in which two successive electrons enter the dot at very close values of the chemical potential. In the strongly correlated regime these

T. Dahm, D. Manske, L. Tewordt

We calculate the c-axis infrared conductivity $σ_c(ω)$ in underdoped cuprate superconductors for spinfluctuation exchange scattering within the CuO$_2$-planes including a phenomenological d-wave pseudogap of amplitude $E_g$. For temperatures decreasing below a temperature $T^* \sim E_g/2$, a gap for $ω< 2E_g$ develops in $σ_c(ω)$ in the incoherent (diffuse)

Ramandeep S. Johal, Renuka Rai

A nonextensive thermostatic approach to chaotic dynamical systems is developed by expressing generalized Tsallis distribution as escort distribution. We explicitly show the thermodynamic limit and also derive the Legendre Transform structure. As an application, bit variance is calculated for ergodic logistic map. Consistency of the formalism demands a relati

Chang-Soo Park, Sahng-Kyoon Yoo, Dal-Ho Yoon

We investigate the escape rate of a biaxial spin particle with an arbitrarily dierected magnetic field in the easy plane, described by Hamiltonian ${\cal H} = -AS_z^2 - BS_x^2 -H_x S_x -H_z S_z, (A>B>0)$. We derive an effective particle potential by using the method of particle mapping. With the help of the criterion for the presence of a first-order quantum

Ananias G. Tomboulides, Victor Yakhot

We consider a convection process in a thin loop. At $Ra=Ra^{\prime}_{cr}$ a first transition leading to the generation of corner vortices is observed. At higher $Ra$ a coherent large-scale flow, which persists for a very long time, sets up. The mean velocity $\bar{v}$, mass flux $\dm$, and the Nusselt number $Nu$ in this flow scale with $Ra$ as $\bar{v} \pro

Der-San Chuu, De-Hone Lin

The Green&#39;s functions of the two and three-dimensional relativistic Aharonov-Bohm (A-B) systems are given by the path integral approach. In addition the exact radial Green&#39;s functions of the spherical A-B quantum billiard system in two and three-dimensional are obtained via the perturbation techanique of $δ$-function.

Peter Grassberger, Thomas Schreiber

We argue that Gaspard and coworkers do not give evidence for microscopic chaos in the sense in which they use the term. The effectively infinite number of molecules in a fluid can generate the same macroscopic disorder without any intrinsic instability. But we argue also that the notion of chaos in infinitely extended systems needs clarification: In a wider

Andrew H. Jaffe, Marc Kamionkowski, Limin Wang

We calculate the detectability of the polarization of the cosmic microwave background (CMB) as a function of the sky coverage, angular resolution, and instrumental sensitivity for a hypothetical experiment. We consider the gradient component of the polarization from density perturbations (scalar modes) and the curl component from gravitational waves (tensor

Kandaswamy Subramanian

We explore the dynamical restrictions on the structure of dark matter halos through a study of cosmological self-similar gravitational collapse solutions. A fluid approach to the collisionless dynamics of dark matter is developed and the resulting closed set of moment equations are solved numerically including the effect of halo velocity dispersions (both ra

Kandaswamy Subramanian, Renyue Cen, Jeremiah P. Ostriker

During hierarchical clustering, smaller masses generally collapse earlier than larger masses and so are denser on the average. The core of a small mass halo could be dense enough to resist disruption and survive undigested, when it is incorporated into a bigger object. We explore the possibility that a nested sequence of undigested cores in the center of the

T. Yaqoob, I. M. George, K. Nandra, T. J. Turner

We report the results from an \asca observation of the QSO PKS 2149-306 (z=2.345). We detect an emission line centered at $\sim 17$ keV in the quasar frame. Line emission at this energy has not been observed in any other active galaxy or quasar to date. We present evidence rejecting the possibility that this line is the result of instrumental artifacts, or a

Lev Titarchuk, Vladimir Osherovich, Sergey Kuznetsov

Precise simultaneous measurements of the frequencies of the two kiloHertz quasi-periodic oscillations (referred in the literature as upper and lower kHz QPOs) cast doubts on the validity of the simple beat-frequency interpretation and some of the modifications introduced to explain the results of the varying frequency difference. A new model explains the var

F. E. Bauer, C. L. Sarazin

We use new ASCA observations and archival ROSAT Position Sensitive Proportional Counter (PSPC) data to determine the X-ray spectral properties of the intracluster gas in Abell 644. From the overall spectrum, we determine the average gas temperature to be 8.64 (+0.67,-0.56) keV, and an abundance of 0.32 (+/-0.04) $Z_{\odot}$. The global ASCA and ROSAT spectra

Andrei Gruzinov

I have shown that the enhancement of fusion rates in stars due to electrostatic screening does not depend on the Gamow energy of the fusing nuclei (in the classical weak screening limit). Opher and Opher have recently published an ApJ paper claiming that my proof is wrong. I show here that their arguments are incorrect.

E. L. Zager, R. J. Wilkes, J. J. Lord

Spot density is commonly used as an indication of shower energy in emulsion chambers. In a system originally developed for JACEE analysis, the optical density of a spot on x-ray film is estimated from macroscopic digital images. The spot&#39;s size is used to compensate for the lack of dynamic range obtainable with digital imaging hardware. These densities a

G. E. Brown, C. -H. Lee, H. A. Bethe

We suggest that high-mass black holes; i.e., black holes of several solar masses, can be formed in binaries with low-mass main-sequence companions, provided that the hydrogen envelope of the massive star is removed in common envelope evolution which begins only after the massive star has finished He core burning. Our evolution scenario naturally explains the

Shoko Sakai, Jeremy R. Mould, Shaun M. G. Hughes, John P. Huchra

This paper presents the calibration of BVRIH$ Tully-Fisher relations based on Cepheid distances to 21 galaxies within 25 Mpc, and 23 clusters within 10,000 km/s. These relations have been applied to several distant cluster surveys in order to derive a value for the Hubble constant, H0, mainly concentrating on an I-band all-sky survey by Giovanelli and collab

J. G. Cramer, S. R. Elliott, J. F. Wilkerson, R. J. Wilkes

The number and density of schools in the Seattle area is convenient for the study of distributed particle showers produced at the top of the atmosphere by ultra-high energy (about $10^{20}$ eV) cosmic rays. We are forming a collaboration for the development of a distributed detector network to study air showers from such ultra-high energy cosmic rays. We cal

Ben Sugerman, F. J. Summers, Marc Kamionkowski

The angular momentum of galaxies is routinely ascribed to a process of tidal torques acting during the early stages of gravitational collapse, and is predicted from the initial mass distribution using second-order perturbation theory and the Zel&#39;dovich approximation. We have tested this theory for a flat hierarchical cosmogony using a large N-body simula

M. Villar-Martin, R. A. E. Fosbury, L. Binette, C. N. Tadhunter

We present UV spectra of a small sample of high redshift active galaxies: the hyperluminous, gravitationally lensed system SMM J02399-0136 (z=2.8) and three powerful radio galaxies (z~2.5). Extended continuum and emission lines are detected in all objects. The three radio galaxies present typical spectra with dominant Lya and weaker CIV1550, HeII1640 and CII

T. S. Metcalfe, R. E. Nather

We have developed a specialized computational instrument for fitting models of pulsating white dwarfs to observations made with the Whole Earth Telescope. This metacomputer makes use of inexpensive PC hardware and free software, including a parallel genetic algorithm which performs a global search for the best-fit set of parameters.

SDSS Collaboration, Xiaohui Fan

This paper describes the discovery of seven dwarf objects of spectral type `L&#39; (objects cooler than the latest M dwarfs) in commissioning imaging data taken by the Sloan Digital Sky Survey (SDSS). Low-resolution spectroscopy shows that these objects have spectral types from L0 to L8. Comparison of the SDSS and 2MASS photometry for several of these object

Eamonn Kerins

Two teams are using the Isaac Newton Telescope to conduct a microlensing search for massive compact halo objects (MACHOs) in Andromeda. We discuss both the motivation of the surveys and the obstacles they must overcome. The key to success is the spatial distribution of detected events. We present a detailed simulation of this observable.

Wolfgang Steffen, Jose Alberto Lopez

We propose a new model for the formation of fast, low-ionization emission regions (FLIERs) in planetary nebulae that is able to account for many of their attendant characteristics and circumvent the problems on the collimation/formation mechanisms found in previous studies. In this model, FLIERs are formed in the stagnation zone of partially collimated stell

Jeremy R Mould, John P Huchra, Wendy L Freedman, Robert C Kennicutt

Since the launch of the Hubble Space Telescope nine years ago, Cepheid distances to 25 galaxies have been determined for the purpose of calibrating secondary distance indicators. A variety of these can now be calibrated, and the accompanying papers by Sakai, Kelson, Ferrarese, and Gibson employ the full set of 25 galaxies to consider the Tully-Fisher relatio

N. Menci, A. Cavaliere

We relate the star formation from cold baryons in virialized structures to the X-ray properties of the associated diffuse, hot baryonic component. Our computations use the standard ``semi-analytic&#39;&#39; models to describe i) the evolution of dark matter halos through merging after the hierarchical clustering, ii) the star formation governed by radiative

Noam Soker

Any model for the formation of elliptical planetary nebulae (PNs) should account for the positive correlation between the mass loss rate and the degree of departure from sphericity of the AGB progenitor&#39;s wind. I propose that this correlation results from dust formation above magnetic cool spots. The model deals with elliptical PNs, but not with bipolar

C. Marinoni, G. Giuricin, L. Ceriani

We discuss the real-space reconstruction of the optical galaxy density field in the local Universe (cz < 6000 km/s) as derived from the 7076 galaxies of the Nearby Optical Galaxy (NOG) sample (see Giuricin et al. 1999 in the same volume). NOG is the currently best approximation to a homogeneous all-sky 3D optically selected galaxy sample that probes in great

G. A. Verdoes Kleijn, S. A. Baum, P. T. de Zeeuw, C. P. O&#39;Dea

We present and analyse HST/WFPC2 broad- and narrow-band observations of the central regions of 19 nearby radio-loud early-type galaxies. Together with two more galaxies they form a complete sample of Fanaroff & Riley Type I galaxies. We obtained V- and I-band images and narrow-band images centered on the \HalphaNII emission lines. We use archival data for si

G. Giuricin, C. Marinoni, L. Ceriani, A. Pisani

In order to map the galaxy density field in the local universe, we select the Nearby Optical Galaxy (NOG) sample, which is a distance-limited (cz < 6000 km/s) and magnitude--limited (B < 14 mag) sample of 7076 optical galaxies which covers 2/3 (8.29 sr) of the sky (|b|>20^{\circ}) and has a good completeness in redshift (98%). In order to trace the galaxy de

N. W. Evans, E. J. Kerins

An expression is provided for the self-lensing optical depth of the thin LMC disk surrounded by a shroud of stars at larger scale heights. The formula is written in terms of the vertical velocity dispersion of the thin disk population. If tidal forcing causes 1-5 % of the disk mass to have a height larger than 6 kpc and 10-15 % to have a height above 3 kpc,

W. J. Percival, L. Miller, W. E. Ballinger

The star formation history of the universe shows strong evolution with cosmological epoch. Although we know mergers between galaxies can cause luminous bursts of star formation, the relative importance of such mergers to the global star formation rate (SFR) is unknown. We present a simple analytic formula for the rate at which halos merge to form higher-mass

Edvige Corbelli, Paolo Salucci

We present the 21-cm rotation curve of the nearby galaxy M33 out to a galactocentric distance of 16 kpc (13 disk scale-lengths). The rotation curve keeps rising out to the last measured point and implies a dark halo mass larger than 5 10^{10} solar masses. The stellar and gaseous disks provide virtually equal contributions to the galaxy gravitational potenti

E. A. Richards, E. B. Fomalont, K. I. Kellermann, R. A. Windhorst

We report on the identifications of radio sources from our survey of the Hubble Deep Field and the SSA13 fields, both of which comprise the deepest radio surveys to date at 1.4 GHz and 8.5 GHz respectively. About 80% of the microjansky radio sources are associated with moderate redshift starburst galaxies or AGNs within the I magnitude range of 17 to 24 with

Pedro G. Ferreira, Andrew H. Jaffe

To correctly analyse data sets from current microwave detection technology, one is forced to estimate the sky signal and experimental noise simultaneously. Given a time-ordered data set we propose a formalism and method for estimating the signal and associated errors without prior knowledge of the noise power spectrum. We derive the method using a Bayesian f

Ofer Aharony, Micha Berkooz

We analyze the superconformal theories (SCFTs) which arise in the low-energy limit of N=(4,4) supersymmetric gauge theories in two dimensions, primarily the Higgs branch SCFT. By a direct field theory analysis we find a continuum of &#34;throat&#34;-like states localized near the singularities of the Higgs branch. The &#34;throat&#34; is similar to the &#34;

Graham D. Kribs

A striking consequence of supersymmetry breaking communicated purely via the superconformal anomaly is that the gaugino masses are proportional to the gauge beta functions. This result, however, is not unique to anomaly mediation. We present examples of ``generalized&#39;&#39; gauge-mediated models with messengers in standard model representations that give

Eanna E. Flanagan, S. -H. Henry Tye, Ira Wasserman

We develop a possible cosmology for a Universe with n additional spatial dimensions of variable scale, and an associated scalar field, the radion, which is distinct from the field responsible for inflation, the inflaton. Based on a particular ansatz for the effective potential for the inflaton and radion (which may emerge in string theory), we show that the

D. I. Golosov

An isotropic half-metallic double exchange magnet with a direct superexchange coupling between the localized spins is studied within the spin-wave (1/S) expansion. The momentum dependence of the spin wave spectrum (including quantum corrections) in the ferromagnetic phase at T=0 is investigated. Based on the calculated spin wave spectrum of the canted state,

Jan B. Thomassen

I investigate bosonization in four dimensions, using the smooth bosonization scheme. I argue that generalized chiral ``phases&#39;&#39; of the fermion field corresponding to chiral phase rotations and ``chiral Poincare transformations&#39;&#39; are the appropriate degrees of freedom for bosonization. Smooth bosonization is then applied to an Abelian fermion

Marsha Weaver

Methods of dynamical systems analysis are used to show rigorously that the presence of a magnetic field orthogonal to the two commuting Killing vector fields in any spatially homogeneous Bianchi type VI_0 vacuum solution to Einstein&#39;s equation changes the evolution toward the singularity from convergent to oscillatory. In particular, it is shown that the

J. C. Lee, A. C. Fabian, C. S. Reynolds, W. N. Brandt

We present an analysis of the long RXTE observation of the Seyfert~1 galaxy MCG-6-30-15, taken in July 1997. Our results show that the behaviour is complicated. We find clear evidence from colour ratios and direct spectral fitting that changes to the intrinsic photon index are taking place. Spectral hardening is evident during periods of diminished intensity

F. Karsch, E. Laermann, A. Peikert

The dependence of thermodynamic properties of QCD on the number of quark flavours is investigated. Lattice results for the equation of state are presented for 2, 2+1 and 3 quark flavours. The simulations have been performed with the improved p4-staggered fermion and a Symanzik improved gluon action on lattices of size 16^3 x 4

Frank Milde, Rudolf A. Römer, Michael Schreiber

We study the three-dimensional Anderson model of localization with anisotropic hopping, i.e. weakly coupled chains and weakly coupled planes. In our extensive numerical study we identify and characterize the metal-insulator transition using energy-level statistics. The values of the critical disorder $W_c$ are consistent with results of previous studies, inc

I. V. Anikin, A. E. Dorokhov, Lauro Tomio

The behavior of the transition pion form factor for processes γ^*γ-> π^0 and γ^* γ^* -> π^0 at large values of space-like photon momenta is estimated within the nonlocal covariant quark-pion model. It is shown that, in general, the coefficient of the leading asymptotic term depends dynamically on the ratio of the constituent quark mass and the average virtua

P. Facchi, S. Pascazio

We study the temporal evolution of a three-level system (such as an atom or a molecule), initially prepared in an excited state, bathed in a laser field tuned at the transition frequency of the other level. The features of the spontaneous emission are investigated and the lifetime of the initial state is evaluated: a Fermi &#34;golden rule&#34; still applies