October 1998 arXiv papers — page 17

Ernest Ma, D. P. Roy, Utpal Sarkar

We have constructed an explicit see-saw model containing two singlet neutrinos, one carrying a $(B-3L_e)$ gauge charge with an intermediate mass scale of $\sim O(10^{10})$ GeV along with a sterile one near the GUT (grand unification theory) scale of $\sim O(10^{16})$ GeV. With these mass scales and a reasonable range of Yukawa couplings, the model can natura

Koji Hasegawa, Takeshi Ikeda, Tetsuya Kikuchi

We study a pair of commuting difference operators arising from the elliptic C_2^{(1)}-face model. The operators, whose coefficients are expressed in terms of the Jacobi's elliptic theta function, act on the space of meromorphic functions on the weight space of the C_2 type simple Lie algebra. We show that the space of functions spanned by the level one c

S. Rai Choudhury, Naveen Gaur

We have added some some refrences & given some figures giving results in parameter space allowed by b \to s γ. Conclusions more or less remains unchanged.

GianCarlo Ghirardi

We call attention on the fact that recent unprecedented technological achievements, in particular in the field of quantum optics, seem to open the way to new experimental tests which might be relevant both for the foundational problems of quantum mechanics as well as for investigating the perceptual processes.

L. Vichi, M. Inguscio, S. Stringari, G. M. Tino

Various features of spin-polarized Fermi gases confined in harmonic traps are discussed, taking into account possible perspectives of experimental measurements. The mechanism of the expansion of the gas is explicitly investigated and compared with the one of an interacting Bose gas. The role of interactions on the equilibrium and non equilibrium behaviour of

P. Lanoix, G. Paturel, R. Garnier

We show that the Cepheid PL relation is affected by a Malmquist type bias, the so-called population incompleteness bias. Its calculated slope appears shallower than the true one because of the cutoff in apparent magnitude resulting from the instrumental limiting magnitude. Furthermore, the use of the PL relation, even with the correct slope, leads to underes

D. Ibaceta, E. Calzetta

The objective of this paper is to study the formation of defects in a non equilibrium second order phase transition by means of a numerical solution of the full dynamical equations, and to compare the results with theoretical predictions to be found in the literature. We simulate an instantaneous quench to zero temperature in a type II superconductor, measur

Elcio Abdalla, Roya Mohayaee

The evolution of inhomogeneities in a spherical collapse model is studied by expanding the Einstein equation in powers of inverse radial parameter. In the linear regime, the density contrast is obtained for flat, closed and open universes. In addition to the usual modes, an infinite number of new growing modes are contained in the solutions for pressureless

Marc-Thierry Jaekel, Serge Reynaud

The description of relativistic effects requires a preliminary definition of events localised in space-time while the clocks used for time definition and the fields used in synchronisation or localisation procedures are necessarily quantum systems. We outline an algebraic framework where basic requirements of quantum theory and relativity are consistently de

Paul B. Slater

This paper has been withdrawn for the reasons mentioned in the Comments.

Tomasz Brzezinski

For a given entwining structure $(A,C)_ψ$ involving an algebra $A$, a coalgebra $C$, and an entwining map $ψ: C\otimes A\to A\otimes C$, a category $\M_A^C(ψ)$ of right $(A,C)_ψ$-modules is defined and its structure analysed. In particular, the notion of a measuring of $(A,C)_ψ$ to $(\tA,\tC)_\tpsi$ is introduced, and certain functors between $\M_A^C(ψ)$ and

R. de la Llave, N. Petrov

We consider the electromagnetic field in a cavity with a periodically oscillating perfectly reflecting boundary and show that the mathematical theory of circle maps leads to several physical predictions. Notably, well-known results in the theory of circle maps (which we review briefly) imply that there are intervals of parameters where the waves in the cavit

J. M. Aguirregabiria, Ll. Bel, A. Hernandez, M. Rivas

We present a C program to compute by successive approximations the regular order reduction of a large class of ordinary differential equations, which includes evolution equations in electrodynamics and gravitation. The code may also find the regular order reduction of delay-differential equations.

F. Ritz, H. Arenhoevel

Rescattering effects in coherent eta photoproduction on the deuteron are studied in the region of the S_11(1535) resonance. For the elementary reaction mechanism on the nucleon, an effective isobar model with inclusion of resonances and Born terms is used. The resonance parameters are fixed by considering pion photoproduction only. For the coherent eta produ

M. Del Estal, M. Centelles, X. Viñas

We perform Hartree calculations of symmetric and asymmetric semi-infinite nuclear matter in the framework of relativistic models based on effective hadronic field theories as recently proposed in the literature. In addition to the conventional cubic and quartic scalar self-interactions, the extended models incorporate a quartic vector self-interaction, scala

A. N. Kvinikhidze, B. Blankleider

We present a unified description of the relativistic piNN and gamma-piNN systems where the strong interactions are described non-perturbatively by four-dimensional integral equations. A feature of our approach is that the photon is coupled in all possible ways to the strong interaction contributions. Thus the hadronic processes NN -> NN, NN -> pid, pid -> pi

W. C. Haxton

I discuss three issues relevant to solar neutrino flux measurements: cross section uncertainties in pp chain reactions, uncertainties in the GALLEX/SAGE response to 7Be and 51Cr neutrinos, and the implications of helioseismology for nonstandard suns with mixed cores. A few comments are also offered on electron neutrino to tauon neutrino oscillations, cosmolo

A. M. Bernstein, M. M. Pavan

Experiments on pion (Goldstone Boson) photoproduction from the nucleon tests the ability to make QCD predictions at confinement scale energies. Experiments with both polarized beams and targets have the potential sensitivity to demonstrate the dynamic isospin breaking effects of the up and down quark mass difference, whereas experiments on Compton scattering

Matthew Leingang

For a Lie group G, we seek the right definition of a "moment space" for G. One axiom is clear, involving a closed equivariant three-form. We construct this form for symmetric spaces associated to a symmetric pair (H,G) with an additional structure. Furthermore, we prove a decomposition theorem for these pairs over a compact, connected, and semisimple

I. Nezhmetdinov

In the paper new representations are obtained for duals and dual hulls of the classes of analytic functions. The Ruscheweyh duality principle is shown to hold under somewhat weaker assumptions. For a compact class of functions its subclass is constructed having the same dual as the original one.

Wladyslaw Marcinek

An algebraic formalism for the study of a system of charged particles interacting with an external quantum field is developed. The notion of monoidal categories with duality is used for the description of composite systems and corresponding quantum statistics. The Fock space representation is also discussed.

Carlos Simpson

We look at strict $n$-groupoids and show that if $\Re$ is any realization functor from the category of strict $n$-groupoids to the category of spaces satisfying a minimal property of compatibility with homotopy groups, then there is no strict $n$-groupoid $G$ such that $\Re (G)$ is the $n$-type of $S^2$ (for $n\geq 3$). At the end we speculate on how one mig

Carlos Simpson

We show that if $2k\geq n$, then a k-connected weak n-category $A$ can be ``delooped'' to a k+1-connected weak n+1-category $Y$ with $Hom_Y(y,y)\cong A$. This is the essential part of the ``stabilization hypothesis'' of Baez and Dolan q-alg/9503002, math/9802029.

Emilia Mezzetti, Dario Portelli

It is known that the smooth rational threefolds of P^5 having a rational non-special surface of P^4 as general hyperplane section have degree d=3,... ,7. We study such threefolds X from the point of view of linear systems of surfaces in P^3, looking in each case fosr an explicit description of a birational map from P^3 to X. For d=3,..., 6 we prove that ther

Ugo Bruzzo, Vladimir Pestov

We discuss the problem of finding an analogue of the concept of a topological space in supergeometry, motivated by a search for a procedure to compactify a supermanifold along odd coordinates. In particular, we examine the topologies naturally arising on the sets of points of locally ringed superspaces, and show that in the presence of a nontrivial odd secto

Lawrence Breen

We associate to a braided 2-stack ${\cal C}$ a torsor, endowed with a symmetric cube structure (or $Σ$-structure), whose triviality is equivalent to the existence on ${\cal C}$ of a fully symmetric monoidal structure. In order to perform the analogous construction for braided 4-stacks, it is necessary to introduce the notion of a $Γ_3$-torsor pair, which is

Arnaud Beauville

Let X be a compact Kaehler manifold. We expect that any direct sum decomposition of the tangent bundle T(X) comes from a splitting of the universal covering space of X as a product of manifolds, in such a way that the given decomposition of T(X) lifts to the canonical decomposition of the tangent bundle of a product. We prove this assertion when X is a Kaehl

Luiz A. Ferreira, Erica E. Leite

We construct local zero curvature representations for non-linear sigma models on homogeneous spaces, defined on a space-time of any dimension, following a recently proposed approach to integrable theories in dimensions higher than two. We present some sufficient conditions for the existence of integrable submodels possessing an infinite number of local conse

Charles B. Thorn

The large $N_c$ limit of Yang-Mills gauge theory is the dynamics of a closed gluonic chain, but this fact does not obviate the inherently strong coupling nature of the dynamical problem. However, we suggest that a single link in such a chain might be reasonably described in the quasi-perturbative language of gluons and their interactions. To implement this i

S. Ferrara, M. Porrati, A. Zaffaroni

It is argued that N=6 supergravity on $AdS_5$, with gauge group $SU(3)\times U(1)$ corresponds, at the classical level, to a subsector of the ``chiral'' primary operators of N=4 Yang-Mills theories. This projection involves a ``duality transformation'' of N=4 Yang-Mills theory and therefore can be valid if the coupling is at a self-dual point

Iver Brevik, V. N. Marachevsky, Kimball A. Milton

We show that the Casimir, or zero-point, energy of a dilute dielectric ball, or of a spherical bubble in a dielectric medium, coincides with the sum of the van der Waals energies between the molecules that make up the medium. That energy, which is finite and repulsive when self-energy and surface effects are removed, may be unambiguously calculated by either

Y. Brihaye, T. N. Tomaras

We study in a systematic way all static solutions of the Goldstone model in 1+1 dimension with a periodicity condition on the spatial coordinate. The solutions are presented in terms of the standard trigonometric functions and of Jacobi elliptic functions. Their stability analysis is carried out, and the complete list of classical stable quasi-topological so

E. Abdalla, N. Alves

After presenting a survey of theoretical results concerning the structure of two-dimensional QCD, we present a numerical study related to the mass eigenstates and the decay amplitudes of higher mesonic states. We discuss in detail the fate of important dynamical points such as stability of the spectrum and the problem of screening versus confinement in this

J. L. Hewett

The principle components of the Standard Model and the status of their experimental verification are reviewed. Lectures given at TASI97: Supersymmetry, Supergravity, and Supercolliders}, Boulder, CO, June 1997.

J. Hein

I give an overview of phenomenological heavy quark results obtained in NRQCD on the lattice. In particular I discuss the bottomonium and the b-light hadron spectrum. I also review recent results on the decay constants f_B and f_B_s.

F. Klingl, T. Waas, W. Weise

Models based on chiral SU(3)_L \otimes SU(3)_R symmetry and vector meson dominance suggest an attractive potential for the $ω$-meson in a nuclear medium. We discuss the feasibility of producing nuclear bound states of $ω$-mesons using $(d,^3He)$ and pion induced reactions on selected nuclear targets.

Bing An Li

Based on an effective chiral theory of pseudoscalar, vector, and axial-vector mesons, the coefficients of the chiral perturbation theory are predicted. There is no new parameter in these predictions.

Robert Bluhm, Alan Kostelecky, Neil Russell

A theoretical analysis is performed of Penning-trap experiments comparing protons and antiprotons to test CPT and Lorentz symmetry through measurements of anomalous magnetic moments and charge-to-mass ratios. Possible CPT and Lorentz violations arising at a fundamental level are treated in the context of a general extension of the standard model of particle

W. Buchmüller, T. Yanagida

The mass hierarchies of quarks and charged leptons as well as a large $\n_\m$-$\n_\t$ mixing angle are naturally explained by the Frogatt-Nielsen mechanism with a nonparallel family structure of chiral charges. We extend this mechanism to right-handed neutrinos. Their out-of-equilibrium decay generates a cosmological baryon asymmetry whose size is quantized

F. Becattini

The estimates of overall strange quark production in high energy e+e-, pp and ppbar collisions by using the statistical-thermal model of hadronisation are presented and compared with previous works. The parametrization of strangeness suppression within the model is discussed. Interesting regularities emerge in the strange/non-strange produced quark ratio whi

Tuomas Multamaki, Iiro Vilja

The possibility of electroweak baryogenesis is considered within the framework of a left-right supersymmetric model. It is shown that for a range of parameters the large sneutrino VEV required for parity breaking varies at the electroweak phase transition leading to a production of baryons. The resulting baryon to entropy ratio is approximated to be ${n_B\ov

L. V. Fil'kov, V. L. Kashevarov

The Compton scattering on a charged pion is studied using the dispersion relations. Unknown mass, full width and decay width into γγof the sigma meson are found from a fit to the experimental data for the process γ+γ\to π^0+π^0. These parameters are used for the calculation of the cross section of the Compton scattering on the charged pion. The analysis of t

M. Masip

In supersymmetric models the presence of Higgs triplets introduce new quartic interactions for the doublets that may raise the mass of the lightest CP-even field up to 205 GeV. We show that the complete effect of the triplets can be understood by decoupling them from the minimal sector and then analyzing the vacuum and the spectrum of the two-Higgs doublet m

Norbert Straumann

Apart from a few remarks on lattice systems with global or gauge symmetries, most of this talk is devoted to some interesting ancient examples of symmetries and their breakdowns in elasticity theory and hydrodynamics. Since Galois Theory is in many ways the origin of group theory as a tool to analyse (hidden) symmetries, a brief review of this profound mathe

P. Ko

The charm content in $η'$ is estimated using the QCD U(1) axial anomaly applied to $b\to s g g \to η' s$. We find $f_{η'}^{(c)} \approx - 3.1$ MeV for $m_c = 1.3$ GeV. Our estimate agrees with other independent methods by Feldmann and Kroll, and Araki, Musakhanov and Toki. The resulting branching ratios for $B \to η' K$ in the generalized fac

I. Dadic

Long standing problem in out-of-equilibrium thermal field theories are pinching singularities. We find that the expressions suspect of pinching require loop particles to be on the mass shell. This fact, with the help of threshold effect and similar effect due to spin, leads to the elimination of pinching in single self-energy insertion approximation to propa

K. Lang, J. Ting, V. Vassilakopoulos

We present a new technique of direct measurement of wire tensions in wire chambers. A specially designed circuit plucks the wire using the Lorentz force and measures the frequency of damped transverse oscillations of the wire. The technique avoids the usual time-consuming necessity of tuning circuit parameter to a resonance. It allows a fast and convenient d

K. Zuber

The motivation for possible future long baseline neutrino experiments is discussed. The proposed experiments as well as their physics potential is reviewed.

The OPAL Collaboration, G. Abbiendi et al

Photonic events with large missing energy have been observed in e+e- collisions at centre-of-mass energies of 130, 136 and 183 GeV collected in 1997 using the OPAL detector at LEP. Results are presented for event topologies with a single photon and missing transverse energy or with an acoplanar photon pair. Cross-section measurements are performed within the

Tonatiuh Matos

Using the Harmonic map ansatz, we reduce the axisymmetric, static Einstein-Maxwell equations coupled with a magnetized perfect fluid to a set of Poisson-like equations. We were able to integrate the Poisson equations in terms of an arbitrary function $M=M(ρ,ζ)$ and some integration constants. The thermodynamic equation restricts the solutions to only some st

Sukanta Bose, Daksh Lohiya

We show that in a generic scalar-tensor theory of gravity, the ``referenced'' quasilocal mass of a spatially bounded region in a classical solution is invariant under conformal transformations of the spacetime metric. We first extend the Brown-York quasilocal formalism to such theories to obtain the ``unreferenced'' quasilocal mass and prove

G. Ortiz, M. Harris, P. Ballone

The stability of different phases of the three-dimensional non-relativistic electron gas is analyzed using stochastic methods. With decreasing density, we observe a {\it continuous} transition from the paramagnetic to the ferromagnetic fluid, with an intermediate stability range ($25\pm 5 \leq r_s\leq 35 \pm 5$) for the {\it partially} spin-polarized liquid.

A. Zheludev, S. Maslov, G. Shirane, I. Tsukada

New neutron diffraction and inelastic scattering experiments are used to investigate in detail the field dependence of the magnetic structure and low-energy spin wave spectrum of the Dzyaloshinskii-Moriya helimagnet Ba_2 Cu Ge_2 O_7. The results suggest that the previously proposed model for the magnetism of this compound (an ideal sinusoidal spin spiral, st

P. Calvani, G. De Marzi, P. Dore, S. Lupi

The infrared absorption of charge density waves coupled to a magnetic background is first observed in two manganites La{1-x}Ca{x}MnO{3} with x = 0.5 and x = 0.67. In both cases a BCS-like gap 2 Delta (T), which for x=0.5 follows the hysteretic ferro-antiferromagnetic transition, fully opens at a finite T{0} < T{Neel}, with 2 Delta(T{0})/kT{c} close to 5. The

H. D. Robinson, B. B. Goldberg, J. L. Merz

Scattering of carriers between spatially separated zero dimensional states has been observed in a system of self-assembled In_{0.55}Al_{0.45}As quantum dots. We believe the interdot tunneling is mediated by localized states below the barrier band edge. The experiment was performed by taking photoluminescence excitation spectra at 4.2K using a near-field scan

Stefan Luding

In a freely cooling granular material fluctuations in density and temperature cause position dependent energy loss. Due to strong local dissipation, pressure and energy drop rapidly and material moves from `hot&#39; to `cold&#39; regions, leading to even stronger dissipation and thus causing the density instability. The assumption of `molecular chaos&#39; is

G. Aggarwal, P. Sen

We report study of recovery dynamics, followed by in-situ resistivity measurement after 100 MeV oxygen ion irradiation, in cold rolled Fe at 300K. Scaling behavior with microstructural density and temperature of sample have been used to establish stress induced defects formed during irradiation as a new type of sink. The dynamics after irradiation has been s

Shoji Yamamoto, Toru Sakai

Static and dynamic structure factors of Heisenberg ferrimagnetic spin chains are numerically investigated. There exist two distinct branches of elementary excitations, which exhibit ferromagnetic and antiferromagnetic aspects. The ferromagnetic feature is smeared out with the increase of temperature, whereas the antiferromagnetic one persists up to higher te

Shoji Yamamoto

Magnetic susceptibilities of spin-$(S,s)$ ferrimagnetic Heisenberg chains are numerically investigated. It is argued how the ferromagnetic and antiferromagnetic features of quantum ferrimagnets are exhibited as functions of $(S,s)$. Spin-$(S,s)$ ferrimagnetic chains behave like combinations of spin-$(S-s)$ ferromagnetic and spin-$(2s)$ antiferromagnetic chai

Shoji Yamamoto

Based on a symmetry argument, we systematically reveal Hartree-Fock broken-symmetry solutions of the one-dimensional two-band extended Peierls-Hubbard model. Performing numerical investigations as well, the possibility of novel density-wave states appearing is argued.

Jian Wang, Hong Guo

We have calculated and statistically analyzed the magnetic-field spectrum (the ``B-spectrum&#39;&#39;) at fixed electron Fermi energy for two quantum dot systems with classically chaotic shape. This is a new problem which arises naturally in transport measurements where the incoming electron has a fixed energy while one tunes the magnetic field to obtain res

H. Okamura, D. Heiman, M. Sundaram, A. C. Gossard

Time-resolved photoluminescence measurements show that the decay time for charged excitons in a GaAs two-dimensional electron gas increases by an order of magnitude at high magnetic fields. Unlike neutral excitons, the charged exciton center-of-mass is spatially confined in a ``magnetically-adjustable quantum dot&#39;&#39; by the cyclotron orbit and the quan

David M. Walker, R. Brown, N. B. Tufillaro

We use radial basis functions to model the input--output response of an electronic device. A new methodology for producing models that accuratly describe the response of the device over a wide range of operating points is introduced. A key to the success of the method is the ability to find a polynomial relationship between the model parameters and the opera

A. M. Selvam, Suvarna Fadnavis

Atmospheric flows exhibit cantorian fractal space-time fluctuations signifying long-range spatiotemporal correlations. A recently developed cell dynamical system model shows that such non-local connections are intrinsic to quantum-like chaos governing flow dynamics. The dynamical evolution of fractal structures can be quantified in terms of ordered energy fl

A. S. Evans

CO observations of 0<z<4 radio galaxies are presented. The L_CO upper limits for the high-redshift powerful radio galaxies (HzPRGs: z > 1, P_408MHz > 10^27 Watts/Hz) are consistent with no evolution in molecular gas (H_2) mass with redshift and/or radio power. Of the low-redshift powerful radio galaxies (LzPRGs: z<0.2, P_408MHz MHz > 10^23.5 W/Hz) observed,

Suzanne M. Linder

Using simulations of the low redshift galaxy population based upon galaxy observations, it is shown (Linder 1998) that the majority of Ly$α$ absorbers at low redshift could arise in low surface brightness (LSB) galaxies. The contribution to absorption from LSB galaxies is large for any galaxy surface brightness distribution which is currently supported by ob

Matthew G. Baring, Alice K. Harding

The complete absence of radio pulsars with periods exceeding a few seconds has lead to the popular notion of the existence of a high period death line. We have recently postulated the existence of another radio quiescence boundary at high magnetic fields ($B\gtrsim 4\times 10^{13}$G) in the upper portion of the period-period derivative diagram, a domain wher

A. S. Evans, D. B. Sanders, J. A. Surace, J. M. Mazzarella

The first detection of CO emission in a Fanaroff-Riley Class II (i.e., edge-brightened radio morphology) radio galaxy is presented. Multi- wavelength (0.36-2.17 micron) imaging of 3C 293 shows it to be a disk galaxy with an optical jet or tidal tail extending towards what appears to be a companion galaxy 28 kpc away via a low surface brightness envelope. The

Matthew G. Baring, Donald C. Ellison, Stephen P. Reynolds, Isabelle Grenier

Supernova remnants (SNRs) are widely believed to be the principal source of galactic cosmic rays. Such energetic particles can produce gamma-rays and lower energy photons via interactions with the ambient plasma. In this paper, we present results from a Monte Carlo simulation of non-linear shock structure and acceleration coupled with photon emission in shel

R. I. Davies, W. Hackenberg, T. Ott, A. Eckart

The sodium laser guide star adaptive optics system ALFA, which is installed at the Calar Alto 3.5-m telescope, has been undergoing an intensive optimisation phase. Observations using natural guide stars that are presented in this paper, show that for bright stars (V~<8) it is now possible to reach K-band Strehl ratios in excess of 60% and to easily resolve b

G. Paturel, P. Lanoix, P. Teerikorpi, G. Theureau

New distances, larger than previous ones, have been obtained for M 31 and M 81 based on the geometrical zero-point of the Cepheid Period-luminosity relation provided by the HIPPARCOS satellite. By combining them with independent determinations we define reasonable ranges for the distances of these important calibrating galaxies. On this basis, we determine t

Volker Beckmann

We present analysis of a new flux limited sample of 72 X-ray selected BL Lacertae objects with known redshifts for 59 of them. We find the more X-ray dominated BL Lac having negative evolution with redshift, while intermediate objects show no evolution at all. X-ray dominated objects show higher X-ray luminosities and flatter X-ray spectra than the intermedi

Sadanori Okamura, Naoki Yasuda, Kazuhiro Shimasaku, Masafumi Yagi

We show that the growth curves of galaxies can be used to determine their bulge and disk parameters and bulge-to-total luminosity ratios, in addition to their conventional asymptotic magnitudes, provided that the point spread function is accurately known and signal-to-noise ratio is modest (S/N$\gtrsim30$). The growth curve is a fundamental quantity that mos

Bruce G. Elmegreen, David Block

The V-K colours along the minor axes of spiral galaxies typically change from red to blue with increasing distance, giving the impression that the near side is systematically screened by dust. Such a preferred orientation for dust screens is unlikely. Here we show that common extinction from the embedded dust layer in an exponential disk has the same effect,

J. M. Stil, F. P. Israel

We have studied the relation between HI linewidth and optical luminosity in two samples of dwarf galaxies, with special attention to the accuracy of the inclination correction. The first sample consists of rotationally supported galaxies, and has DDO 154 as a prototype. They have HI linewidths significantly larger than predicted by an extrapolation of the Tu

T. Oosterbroek, A. N. Parmar, E. Kuulkers, T. Belloni

We report results of five pointed BeppoSAX observations of the black hole candidate 4U 1630-47 during part of its 1998 outburst when the 2-10 keV source luminosity decreased from 2.1x10^38 erg/s (for an assumed distance of 10 kpc) by a factor of ~7. The 2-200 keV spectrum can be modeled by a soft multi-temperature disk blackbody and a hard power-law. During

Y. Dabrowski, M. P. Hobson, A. N. Lasenby, C. J. L. Doran

A new method for modelling spherically symmetric inhomogeneities is applied to the formation of clusters in an expanding Universe. We impose simple initial velocity and density perturbations of finite extent and we investigate the subsequent evolution of the density field. Photon paths are also calculated, allowing a detailed consideration of gravitational l

Rosanne Di Stefano, Richard A. Scalzo

In the companion paper we began the task of systematically studying the detection of planets in wide orbits ($a > 1.5 R_E$) via microlensing surveys. In this paper we continue, focusing on repeating events. We find that, if all planetary systems are similar to our own Solar System, reasonable extensions of the present observing strategies would allow us to d

C. Ledoux, B. Theodore, P. Petitjean, M. N. Bremer

We report observations of the z = 3.87 broad absorption line quasar APM 08279+5255 (Irwin et al. 1998) with the Adaptive Optics Bonnette (AOB) of the Canada-France-Hawaii Telescope. The object is found to be a double source. The separation of the two images is 0.35&#34; +/- 0.02&#34; and the intensity ratio I_{north}/I_{south} = 1.21 +/- 0.25 in the H-band.

Edward Frenkel, Nicolai Reshetikhin

We propose the notion of q-characters for finite-dimensional representations of quantum affine algebras. It is motivated by our theory of deformed W-algebras. We show that the q-characters give rise to a homomorphism from the Grothendieck ring of representations of a quantum affine algebra to a polynomial ring. We conjecture that the image of this homomorphi

Paul B. Slater

Zyczkowski, Horodecki, Sanpera, and Lewenstein (ZHSL) recently proposed a ``natural measure&#39;&#39; on the N-dimensional quantum systems (quant-ph/9804024), but expressed surprise when it led them to conclude that for N = 2 x 2, disentangled (separable) systems are more probable (0.632) in nature than entangled ones. We contend, however, that ZHSL&#39;s (r

Gordon Chalmers, Koenraad Schalm

We compute the imaginary part of scalar four-point functions in the AdS/CFT correspondence relevant to N=4 super Yang-Mills theory. Unitarity of the AdS supergravity demands that the imaginary parts of the correlation functions factorize into products of lower-point functions. We include the exchange diagrams for scalars as well as gravitons and find explici

Steven Abel, Toby Falk

We show that the physical minimum of the Constrained MSSM is only free from dangerous charge and colour breaking minima in the region of parameter space bounded by 110< m_1/2< 400 GeV and 80< m_0< 170 GeV. In the remaining regions, the cosmology is severely constrained.

M. M. Brisudova, L. Burakovsky, T. Goldman

Using an unquenched lattice potential to calculate the spectrum of the bottomonium system, we demonstrate numerically that the effect of pair creation is to produce termination of hadronic Regge trajectories, in contrast to the Veneziano model and the vast majority of phenomenological generalizations. Termination of Regge trajectories may have significant ex

M. Musakhanov

We propose an improvement of the Diakonov-Petrov Effective Action on the basis of the Lee-Bardeen results for the quark determinant in the instanton field. This Improved Effective Action provides proper account of the current quark masses, which is particularly important for strange quarks. This Action is successfully tested by the calculations of the quark

R. Arvieu, P. Rozmej

We remind the properties of the intelligent (and quasi-intelligent) spin states introduced by Aragone et al. We use these states to construct families of coherent wave packets on the sphere and we sketch the time evolution of these wave packets for a rigid body molecule.

S. Basu, W. Dappen, A. Nayfonov

The difference in the adiabatic gradient gamma_1 between inverted solar data and solar models is analyzed. To obtain deeper insight into the issues of plasma physics, the so-called ``intrinsic&#39;&#39; difference in gamma_1 is extracted, that is, the difference due to the change in the equation of state alone. Our method uses reference models based on two e

A. A. Andrianov, M. V. Ioffe, D. N. Nishnianidze

A class of integrable 2-dim classical systems with integrals of motion of fourth order in momenta is obtained from the quantum analogues with the help of deformed SUSY algebra. With similar technique a new class of potentials connected with Lax method is found which provides the integrability of corresponding 2-dim hamiltonian systems. In addition, some inte

T. Jungwirth, W. A. Atkinson, B. H. Lee, A. H. MacDonald

We develop a mean-field theory of carrier-induced ferromagnetism in diluted magnetic semiconductors. Our approach represents an improvement over standard RKKY model allowing spatial inhomogeneity of the system, free-carrier spin polarization, finite temperature, and free-carrier exchange and correlation to be accounted for self-consistently. As an example, w

Manoj Kaplinghat, Robert J. Scherrer, Michael S. Turner

Any time variation in the fine-structure constant alters the ionization history of the universe and therefore changes the pattern of cosmic microwave background fluctuations. We calculate the changes in the spectrum of these fluctuations as a function of the change in the fine-structure constant, and we find that these changes are dominated by the change in

Debashish Chowdhury, Andreas Schadschneider

We propose a cellular automata model for vehicular traffic in cities by combining (and appropriately modifying) ideas borrowed from the Biham-Middleton-Levine (BML) model of city traffic and the Nagel-Schreckenberg (NS) model of highway traffic. We demonstrate a phase transition from the &#34;free-flowing&#34; dynamical phase to the completely &#34;jammed&#3

M. E. Gomez, G. K. Leontaris, S. Lola, J. D. Vergados

U(1) family symmetries have led to successful predictions of the fermion mass spectrum and the mixing angles of the hadronic sector. In the context of the supersymmetric unified theories, they further imply a non-trivial mass structure for the scalar partners, giving rise to new sources of flavor violation. In the present work, lepton flavor non-conserving p

J. H. Field

Standard Model fits are performed on the most recent leptonic and b quark Z decay data from LEP and SLD, and FERMILAB data on top quark production, to obtain $m_t$ and $m_H$. Poor fits are obtained, with confidence levels $\simeq$ 2%. Removing the b quark data improves markedly the quality of the fits and reduces the 95% CL upper limit on $m_H$ by $\simeq$ 5

P. Abbamonte, C. A. Burns, E. D. Isaacs, P. M. Platzman

We report resonant inelastic x-ray measurements of insulating La$_2$CuO$_4$ and Sr$_2$CuO$_2$Cl$_2$ taken with the incident energy tuned near the Cu K absorption edge. We show that the spectra are well described in a shakeup picture in 3rd order perturbation theory which exhibits both incoming and outgoing resonances, and demonstrate how to extract a spectra

UKQCD Collaboration, M. Foster, C. Michael

We discuss lattice methods to obtain the derivatives of a lattice meson mass with respect to the bare sea and valence quark masses. Applications are made to quenched and dynamical fermion configurations. We find evidence for significant differences between quenched and dynamical fermion configurations. We discuss how to relate dependence on the bare lattice

Won Tae Kim

The two-dimensional anti-de Sitter space(AdS_2) is constructed in terms of the CGHS model. The geometric solutions are composed of the AdS vacuum and the AdS black hole which are locally equivalent but distinguishable by their mass. The infalling classical fields do not play any role but the quantum back reaction is crucial in the formation of the AdS vacuum

Vesselin Petkov

The purpose of this paper is twofold - to demonstrate that in the gravitational redshift it is the frequency a photon that is constant, and to describe the mechanism responsible for the change of its wavelength.

F. Siddhartha Guzman, Tonatiuh Matos

We present a model for the dark matter in spiral galaxies, which is a result of a static and axial symmetric exact solution of the Einstein-Dilaton theory. We suposse that dark matter is a scalar field endowed with a scalar potential. We obtain that a) the effective energy density goes like $1/(r^2+r_{c}^{2})$ and b) the resulting circular velocity profile o

M. B. Tully, G. C. Joshi

We calculate the exact tree-level scalar mass matrices resulting from symmetry breaking using the most general gauge-invariant scalar potential of the 331 model, both with and without the condition that lepton number is conserved. Physical masses are also obtained in some cases, as well as couplings to standard and exotic gauge bosons.

S. A. Bass, M. Gyulassy, H. Stoecker, W. Greiner

A critical review on signatures of Quark-Gluon-Plasma formation is given and the current (1998) experimental status is discussed. After giving an introduction to the properties of QCD matter in both, equilibrium- and non-equilibrium theories, we focus on observables which may yield experimental evidence for QGP formation. For each individual observable the d