May 2000 arXiv papers — page 16

Leonid Prigozhin, Boris Zaltzman

We consider a modified BCRE model for pile surface dynamics (Bouchaud, Cates, Ravi Prakash, and Edwards, J. Phys. I France, v. 4, p. 1383, 1994) and show that in the long-scale limit this model converges to a quasistationary model of pile growth in the form of an evolutionary variational inequality (Prigozhin, Phys. Rev. E, v. 49, p. 1161, 1994).

Jung-Woo Yoo, Han-Yong Choi

We calculate the optical conductivity, $σ(ω)$, in the normal state fullerene superconductors by self-consistently including the impurity scatterings, the electron-phonon and electron-electron Coulomb interactions. The finite bandwidth of the fullerenes is explicitely considered, and the vertex corection is included $a$ $la$ Nambu in calculating the renormali

T. Kobayashi, T. Shimbori

Statistical mechanics for states with complex eigenvalues, which are described by Gel'fand triplet and represent unstable states like resonances, are discussed on the basis of principle of equal ${\it a priori}$ probability. A new entropy corresponding to the freedom for the imaginary eigenvalues appears in the theory. In equilibriums it induces a new ph

Shu-Chiuan Chang, Robert Shrock

We present exact calculations of the zero-temperature partition function (chromatic polynomial) and $W(q)$, the exponent of the ground-state entropy, for the $q$-state Potts antiferromagnet with next-nearest-neighbor spin-spin couplings on square lattice strips, of width $L_y=3$ and $L_y=4$ vertices and arbitrarily great length $L_x$ vertices, with both free

William Bialek

Many processes in biology, from the regulation of gene expression in bacteria to memory in the brain, involve switches constructed from networks of biochemical reactions. Crucial molecules are present in small numbers, raising questions about noise and stability. Analysis of noise in simple reaction schemes indicates that switches stable for years and switch

Pritiraj Mohanty, Richard A. Webb

We report the observation of an anomalous magnetoresistance in extremely dilute quasi-one-dimensional AuFe wires at low temperatures, along with a hysteretic background at low fields. The Kondo resistivity does not show the unitarity limit down to the lowest temperature, implying uncompensated spin states. We suggest that the anomalous magnetoresistance may

Pritiraj Mohanty

We consider the correlation of the electromagnetic field to determine spatial coherence inside a sonoluminescing bubble. We explicitly calculate the first order correlation function for two limiting cases of the excitation field: a blackbody spectrum and a discrete multifrequency spectrum. The correlation length for blackbody fields at temperatures between 3

Shu-Chiuan Chang, Robert Shrock

partial abstract: The $q$-state Potts model partition function (equivalent to the Tutte polynomial) for a lattice strip of fixed width $L_y$ and arbitrary length $L_x$ has the form $Z(G,q,v)=\sum_{j=1}^{N_{Z,G,λ}}c_{Z,G,j}(λ_{Z,G,j})^{L_x}$, where $v$ is a temperature-dependent variable. The special case of the zero-temperature antiferromagnet ($v=-1$) is th

Walter F. Brisken, John M. Benson, A. J. Beasley, Edward B. Fomalont

A new technique has been developed to remove the ionosphere's distorting effects from low frequency VLBI data. By fitting dispersive and non-dispersive components to the phases of multi-frequency data, the ionosphere can be effectively removed from the data without the use of {\em a priori} calibration information. This technique, along with the new gati

M. Asplund

Using realistic hydrodynamical simulations of the solar surface convection as 3D, time-dependent, inhomogeneous model atmospheres, the solar photospheric Si abundance has been determined to be log Si = 7.51 +- 0.04. This constitutes a difference of 0.04 dex compared with previous estimates based on the 1D Holweger-Müller (1974) model, of which half is attrib

M. Asplund, AA. Nordlund, R. Trampedach, R. F. Stein

The solar photospheric Fe abundance has been determined using realistic ab initio 3D, time-dependent, hydrodynamical model atmospheres. The study is based on the excellent agreement between the predicted and observed line profiles directly rather than equivalent width, since the intrinsic Doppler broadening from the convective motions and oscillations provid

M. Asplund, AA. Nordlund, R. Trampedach, C. Allende Prieto

Realistic ab-initio 3D, radiative-hydrodynamical convection simulations of the solar granulation have been applied to FeI and FeII line formation. In contrast to classical analyses based on hydrostatic 1D model atmospheres the procedure contains no adjustable free parameters but the treatment of the numerical viscosity in the construction of the 3D, time-dep

M. Asplund, H. -G. Ludwig, AA. Nordlund, R. F. Stein

The computationally demanding nature of radiative-hydrodynamical simulations of stellar surface convection warrants an investigation of the sensitivity of the convective structure and spectral synthesis to the numerical resolution and dimension of the simulations, which is presented here. With too coarse a resolution the predicted spectral lines tend to be t

F. Governato, S. Ghigna, B. Moore, T. Quinn

We combine semi-analytical methods with a ultra-high resolution simulation of a galaxy cluster (of mass 2.3 10^14h-1Msolar, and 4 10^6 particles within its virial radius) formed in a standard CDM universe to study the spatial distribution and orbital properties of the present-day descendents of Lyman Break Galaxies (LBGs). At the present time only five (out

G. A. Wolf-Chase, M. Barsony, J. O'Linger

We present sensitive, large-scale maps of the CO J=1-0 emission of the L1448 dark cloud. These maps were acquired using the On-The-Fly capability of the NRAO 12-meter telescope. CO outflow activity is seen in L1448 on parsec-scales for the first time. Careful comparison of the spatial and velocity distribution of our high-velocity CO maps with previously pub

D. Proga, J. M. Stone, T. R. Kallman

We present the results of time-dependent hydrodynamic calculations of line- driven winds from accretion disks in AGN. To calculate the radiation force, we take into account radiation from the disk and the central engine. The gas temperature and ionization state in the wind are calculated self-consistently. We find that a disk accreting onto a 10^8 MSUN black

Sidney van den Bergh

In 1900 it was believed that almost 100% of the mass of the Universe resided in stars. Now, in the year 2000, such stars (and cold gas) are known to account for only ~1% its mass. The remaining mass of the Universe is thought to reside in hot baryons (~3%), cold dark matter (~30%) and dark energy (~66%). The present paper traces the evolution of our thinking

U. Geppert, D. Page, T. Zannias

An analysis of the role of general relativistic effects on the decay of neutron star's magnetic field is presented. At first, a generalized induction equation on an arbitrary static background geometry has been derived and, secondly, by a combination of analytical and numerical techniques, a comparison of the time scales for the decay of an initial dipol

Robert J. Brunner, Alex S. Szalay, Andrew J. Connolly

Measuring the evolution in the clustering of galaxies over a large redshift range is a challenging problem. We have developed a new technique which uses photometric redshifts to measure the angular correlation function in redshift shells. This novel approach minimizes the galaxy projection effect inherent in standard angular correlation measurements, and all

Luca Tancredi Barone, Andreas Heithausen, Susanne Huettemeister, Thomas Fritz

Blue compact dwarf galaxies (BCDGs) are currently undergoing strong bursts of star formation. Nevertheless, only a few of them have been clearly detected in CO, which is thought to trace the "fuel" of star formation: H_2. In this paper, we present a deep search for CO J=1-->0 and J=2-->1 emission lines in a sample of 8 BCDGs and two companions. Only

Jose A. Pons, J. Ma. Ibanez, Juan A. Miralles

We study the mathematical character of the angular moment equations of radiative transfer in spherical symmetry and conclude that the system is hyperbolic for general forms of the closure relation found in the literature. Hyperbolicity and causality preservation lead to mathematical conditions allowing to establish a useful characterization of the closure re

J. Torra, D. Fernandez, F. Figueras

The local velocity field of young stars is dominated by the galactic rotation, the kinematics of the Gould Belt and the nearest OB associations and open clusters, and the kinematics of the spiral structure. We re-examined here this local velocity field by using a large sample of nearby O and B stars from the Hipparcos Catalogue. The high quality astrometric

T. Belloni, S. Migliari, R. P. Fender

We have analyzed in detail a set of Rossi X-ray Timing Explorer (RXTE) observations of the galactic microquasar GRS 1915+105 corresponding to times when quasi-periodic oscillations in the infrared have been reported. From time-resolved spectral analysis, we have estimated the mass accretion rate through the (variable) inner edge of the accretion disk. We com

N. Slonim, R. Somerville, N. Tishby, O. Lahav

A new method for classification of galaxy spectra is presented, based on a recently introduced information theoretical principle, the `Information Bottleneck'. For any desired number of classes, galaxies are classified such that the information content about the spectra is maximally preserved. The result is classes of galaxies with similar spectra, where

Francine R. Marleau, James R. Graham, Michael C. Liu, Stephane Charlot

We present the first infrared color-magnitude diagram (CMD) for the halo of a giant elliptical galaxy. The CMD for the stars in the halo of NGC 5128 (Centaurus A) was constructed from HST NICMOS observations of the WFPC2 CHIP-3 field of Soria et al. (1996) to a 50% completeness magnitude limit of [F160W]=23.8. This field is located at a distance of 08'50

Yutaka Fujita, Masahiro Nagashima, Naoteru Gouda

In order to constrain parameters in galaxy formation theories, especially those for a star formation process, we investigate cold gas in elliptical galaxies. We calculate the detection rate of cold gas in them using a semi-analytic model of galaxy formation and compare it with observations. We show that the model with a long star formation time-scale (~20 Gy

Joel Silber, Tim Gledhill, Gaspard Duchene, Franccois Menard

We present 1 micron Hubble Space Telescope/NICMOS resolved imaging polarimetry of the GG Tau circumbinary ring. We find that the ring displays east-west asymmetries in surface brightness as well as several pronounced irregularities, but is smoother than suggested by ground-based adaptive optics observations. The data are consistent with a 37 deg system incli

D. Page, U. Geppert, T. Zannias

We investigate the thermal, magnetic and rotational evolution of isolated neutron stars assuming that the dipolar magnetic field is confined to the crust. Our treatment, for the first time, uses a fully general relativistic formalism not only for the thermal but also for the magnetic part, and includes partial general relativistic effects in the rotational p

Inti Pelupessy, Henny J. G. L. M. Lamers, Jorick S. Vink

We have formulated the momentum equation for sectorial line driven winds from rotating stars including: (a) the oblateness of the star, (b) gravity darkening (von Zeipel effect), (c) conservation of angular momentum, (d) line driving specified by the force multiplier parameters (k, alpha, delta), (e) finite disk correction factors for an oblate star with gra

J. S. Deng, Y. L. Qiu, J. Y. Hu, K. Hatano

Low resolution spectra of SN 1999dn at early times are presented and compared with synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW. We find that the spectra of SN 1999dn strongly resemble those of SN 1997X and SN 1984L, and hence we classify it as a Type Ib event. Line-identifications are established through spectru

Peter G. Jonker, Rob P. Fender, Nigel C. Hambly, Michiel van der Klis

We have obtained UKIRT infrared observations of the field of the bright Galactic Z source GX5-1. From an astrometric plate solution tied to Tycho-ACT standards we have obtained accurate positions for the stars in our field which, combined with an accurate radio position, have allowed us to identify the probable infrared counterpart of GX5-1. Narrow-band phot

Jaume Gomis, Thomas Mehen

We study the perturbative unitarity of noncommutative scalar field theories. Field theories with space-time noncommutativity do not have a unitary S-matrix. Field theories with only space noncommutativity are perturbatively unitary. This can be understood from string theory, since space noncommutative field theories describe a low energy limit of string theo

L. D. Paniak, R. J. Szabo

We study the statistical mechanics of random surfaces generated by NxN one-matrix integrals over anti-commuting variables. These Grassmann-valued matrix models are shown to be equivalent to NxN unitary versions of generalized Penner matrix models. We explicitly solve for the combinatorics of 't Hooft diagrams of the matrix integral and develop an orthogo

E. V. Bugaev, K. V. Konishchev

We calculated the energy spectra and the fluxes of electron neutrino emitted in the process of evaporation of primordial black holes (PBHs) in the early universe. It was assumed that PBHs are formed by a blue power-law spectrum of primordial density fluctuations. We obtained the bounds on the spectral index of density fluctuations assuming validity of the st

Shin'ichi Nojiri, Octavio Obregon, Sergei D. Odintsov

5d dilatonic gravity (bosonic sector of gauged supergravity) with non-trivial bulk potential and with surface terms (boundary cosmological constant and trace anomaly induced effective action for brane quantum matter) is considered. For constant bulk potential and maximally SUSY Yang-Mills theory (CFT living on the brane) the inflationary brane-world is const

Sergei V. Ketov

I discuss the symmetry structure of the N=2 supersymmetric extension of the Born-Infeld action in four dimensions, and confirm its interpretation as the Goldstone-Maxwell action associated with partial breaking of N=4 extended supersymmetry down to N=2, by revealing a hidden invariance of the action with respect to two non-linearly realized supersymmetries a

G. L. Bayatian

We examine the logical difficulties that arise when a particle(wave) interferes with itself. We propose to carry out to its full extent a `gedanken' experiment originally proposed by Feynman in order to give an unequivocal experimental proof of the correctness of the wave representation. As an example, we give a corpuscular interpretation of the diffract

M. Hammes, D. Rychtarik, V. Druzhinina, U. Moslener

We report on cooling of an atomic cesium gas closely above an evanescent-wave atom mirror. At high densitities, optical cooling based on inelastic reflections is found to be limited by a density-dependent excess temperature and trap loss due to ultracold collisions involving repulsive molecular states. Nevertheless, very good starting conditions for subseque

B. Zilbergleyt

The article presents new model of equilibrium in open chemical systems suggesting a linear dependence of the reaction shift from equilibrium in presence of the external thermodynamic force. Basic equation of this model contains traditional logarithmic term and a non-traditional parabolic term. At isolated equilibrium the non-traditional term equals to zero t

K. A. Bugaev, M. I. Gorenstein, I. N. Mishustin, W. Greiner

Thermodynamical properties of nuclear matter undergoing multifragmentation are studied within a simplified version of the statistical model. An exact analytical solution has been found for the grand canonical ensemble. Excluded volume effects are taken into account in the thermodynamically self-consistent way. In thermodynamic limit the model exhibits a firs

C. A. Bertulani, D. T. de Paula

The velocity dependence of the stopping power of swift protons and deuterons in low energy collisions is investigated. At low projectile energies the stopping is mainly due to nuclear stopping and charge exchange of the electron. The second mechanism dominates after Ep >=200 eV. A dynamical treatment of the charge exchange mechanism based on two-center elect

Ron M. Adin, Alexander Postnikov, Yuval Roichman

Two actions of the Hecke algebra of type A on the corresponding polynomial ring are studied. Both are deformations of the natural action of the symmetric group on polynomials, and keep symmetric functions invariant. We give an explicit description of these actions, and deduce a combinatorial formula for the resulting graded characters on the coinvariant alge

I. V. Bayak

Stated lemma contains the assertions about isomorphism of exact m-forms and exterior differentials of regular m-maps, of linearly harmonic m-forms and exterior differentials of regular harmonic m-maps, of global minimal (n-m)-surfaces and level (n-m)-surfaces of regular minimal m-maps. It hold in n-dimensional Euclidean space.

Noam D. Elkies

We give a new algorithm using linear approximation and lattice reduction to efficiently calculate all rational points of small height near a given plane curve C. For instance, when C is the Fermat cubic, we find all integer solutions of |x^3+y^3-z^3|<M with 0<x<=y<z<N in heuristic time << L(N) M [where L(X):= (log X)^O(1)] provided M>>N, using only O(log N)

Gen Kuroki, Takashi Takebe

We construct a Gaudin type lattice model as the Wess-Zumino-Witten model on elliptic curves at the critical level. Bethe eigenvectors are obtained by the bosonisation technique.

Ze-sen Yang, Zhining Zhou, Yushu Zhong, Xianhui Li

The problem of renormalisability of the SU(n) theory with massive gauge bosons is reinverstigated in the present work. We expound that the quantization under the Lorentz condition caused by the mass term of the gauge fields leads to a ghost action which is the same as that of the usual SU(n) Yang-Mills theory in the Landau gauge. Furthermore, we clarify that

J. Soffer, O. V. Teryaev

The positivity bound for the transverse asymmetry $A_2$ may be improved and applied for each quark flavor separately. We use it to test the consistency of twist-two approximation for the transverse spin-dependent ($g_T$) and the longitudinal spin-averaged ($F_L$) structure functions. While it is satisfied in the case of $u$ quarks, it might be violated for $

Kirill Melnikov, Timo van Ritbergen

We describe a calculation of the on-shell renormalization factors in QCD and QED at the three loop level. Explicit results for the fermion mass renormalization factor Zm and the on-shell fermion wave function renormalization constant Z2 are given. We find that at O(alpha_s^3) the wave function renormalization constant Z2 in QCD becomes gauge dependent also i

A. Guergachi

Existing procedures for model validation have been deemed inadequate for many engineering systems. The reason of this inadequacy is due to the high degree of complexity of the mechanisms that govern these systems. It is proposed in this paper to shift the attention from modeling the engineering system itself to modeling the uncertainty that underlies its beh

C. C. Abilio, P. Butaud, Th. Fournier, J. Vidal

We report transport measurements on superconducting wire networks which provide the first experimental evidence of a new localization phenomenon induced by magnetic field on a 2D periodic structure. In the case of a superconducting wave function this phenomenon manifests itself as a depression of the network critical current and of the superconducting transi

S. Panyukov, Y. Rabin

We study the effects of thermal flucutations on thin elastic filaments with spontaneous curvature and torsion. We derive analytical expressions for the orientational correlation functions and for the persistence length of helices, and find that this length varies non-monotonically with the strength of thermal fluctuations. In the weak fluctuation regime, the

R A Smith, N K Wilkin

We consider a model of $N$ two-dimensional bosons in a harmonic potential with weak repulsive delta-function interactions. We show analytically that, for angular momentum $L\le N$, the elementary symmetric polynomials of particle coordinates measured from the center of mass are exact eigenstates with energy $N(N-L/2-1)$. Extensive numerical analysis confirms

L. Ghivelder, R. S. Freitas, R. E. Rapp, F. A. B. Chaves

The specific heat of the perovskite manganite La0.78Pb0.22MnO3-d was measured from 0.5 to 25 K. The results yield values of the electronic density of states, the Debye temperature, and the spin-wave stiffness constant of the compound. The magnetic contribution was found to be consistent with the existence of a gap in the spin-wave spectrum, and a phonon term

A. Raghunathan, R. Subrahmanyan

The absolute temperature of the cosmic microwave background (CMB) has been measured at a frequency of 1280 MHz. The observation was made with a modified version of the L-band receiver used in the Giant Metre wavelength Radio Telescope (GMRT): the feed horn was replaced by a corrugated plate and the receiver was placed on the ground, directed at zenith, and s

Eva K Grebel

The star formation histories of Local Group galaxies are summarized. The three large spirals are discussed individually, whereas the discussion of the Local Group dwarfs concentrates on differences and commonalities. While Local Group galaxies exhibit an amazing diversity in their star formation and enrichment histories even within the same morphological typ

Eric F. Bell, Richard G. Bower

We have constructed a family of simple models for spiral galaxy evolution to allow us to investigate observational trends in star formation history with galaxy parameters. The models are used to generate broad band colours from which ages and metallicities are derived in the same way as the data. We generate a grid of model galaxies and select only those whi

Urs Achim Wiedemann

We study the relation between the Baier-Dokshitzer-Mueller-Peigne-Schiff (BDMPS) and Zakharov formalisms for medium-induced gluon radiation off hard quarks, and the radiation off very few scattering centers. Based on the non-abelian Furry approximation for the motion of hard partons in a spatially extended colour field, we derive a compact diagrammatic and e

David B. Wilson

There has been much recent interest in the satisfiability of random Boolean formulas. A random k-SAT formula is the conjunction of m random clauses, each of which is the disjunction of k literals (a variable or its negation). It is known that when the number of variables n is large, there is a sharp transition from satisfiability to unsatisfiability; in the

K. -I. Kondo, T. Shinohara

We show that an effective Abelian gauge theory can be obtained as a renormalizable theory from QCD in the maximal Abelian gauge. The derivation improves in a systematic manner the previous version that was obtained by one of the authors and was referred to as the Abelian-projected effective gauge theory. This result supports the view that we can construct an

Srikanth Sastry

Computer simulations have been employed in recent years to evaluate the configurational entropy changes in model glass-forming liquids. We consider two methods, both of which involve the calculation of the `intra-basin&#39; entropy as a means for obtaining the configurational entropy. The first method involves the evaluation of the intra-basin entropy from t

Shoichi Kawamoto, Naoki Sasakura

We investigate the dynamics of open membrane boundaries in a constant C-field background. We follow the analysis for open strings in a B-field background, and take some approximations. We find that open membrane boundaries do show noncommutativity in this case by explicit calculations. Membrane boundaries are one dimensional strings, so we face a new type of

Janko Gravner, Craig A. Tracy, Harold Widom

We introduce a class of one-dimensional discrete space-discrete time stochastic growth models described by a height function $h_t(x)$ with corner initialization. We prove, with one exception, that the limiting distribution function of $h_t(x)$ (suitably centered and normalized) equals a Fredholm determinant previously encountered in random matrix theory. In

Athanasios N. Petridis

We examine deviations from Boltzmann-Gibbs statistics for partially equilibrated systems of finite size. We find that such systems are characterized by the Levy distribution whose non-extensivity parameter is related to the number of internally equilibrated subsystems and to correlations among them. This concept is applied to Quark-Gluon Plasma formation.

Volker D. Burkert

Status, open questions, and future prospects of the physics of excited nucleons are discussed. Emphasis is on the study of the structure of nucleons via measurements of their electromagnetic transition form factors, the search for &#34;missing&#34; resonances, the spin structure of the nucleon in the resonance region, and connections between the resonance an

Bambi Hu, Changsong Zhou

Nonlinear dynamical systems possessing an invariant subspace in the phase space and chaotic or stochastic motion within the subspace often display on-off intermittency close to the threshold of stability of the subspace. In a class of symmetric systems, the intermittency is symmetry-breaking [Ying-Cheng Lai, Phys. Rev. E {\bf 53}. R4267 (1996)]. We report in

G. G. Amosov, A. S. Holevo, R. F. Werner

A class of problems in quantum information theory, having an elementary formulation but still resisting solution, concerns the additivity properties of various quantities characterizing quantum channels, notably the &#34;classical capacity&#34;, and the &#34;maximal output purity&#34;. All known results, including extensive numerical work, are consistent wit

Spencer Bloch, Hélène Esnault

Homology with values in a connection with possibly irregular singular points on an algebraic curve is defined, generalizing homology with values in the underlying local system for a connection with regular singular points. Integration defines a perfect pairing between de Rham cohomology with values in the connection and homology with values in the dual conne

P. Akueson

We introduce the tangent space on a quantum hyperboloid. We define an action of this tangent space on the corresponding &#34;quantum function space&#34; ${\cal A}$, what converts the elements of the tangent space into &#34;braided vector fields&#34;. The tangent space is shown to be a projective ${\cal A}$-module and we define a quantum (pseudo)metric and a

William H. Rowan

We define abelian extensions of algebras in congruence-modular varieties. The theory is sufficiently general that it includes, in a natural way, extensions of R-modules for a ring R. We also define a cohomology theory, which we call clone cohomology, such that the cohomology group in dimension one is the group of equivalence classes of extensions.

Rajsekhar Bhattacharyya, Debashis Gangopadhyay

Starting from lagrangian field theory and the variational principle, we show that duality in equations of motion can also be obtained by introducing explicit spacetime dependence of the lagrangian. Poincare invariance is achieved precisely when the duality conditions are satisfied in a particular way. The same analysis and criteria are valid for both abelian

Ch. Royon

We present and discuss two different topics where Tevatron and HERA data can be compared directly. A method allowing for a direct comparison of data with theoretical predictions is proposed for forward jet production at HERA. An application to the determination of the effective Pomeron intercept in the BFKL-LO parametrization from $dσ/dx$ data at HERA leads

A. N. Mitra

The `Salpeter Equation&#39; which has long been known as the 3D version of the 4D Bethe-Salpeter Equation under the Instantaneous Approximation, has a well-defined rationale that stems from the half-century old Markov-Yukawa Transversality Principle (MYTP) which not only effects an exact 3D reduction from the original (4D) BS form, but also provides an equal

Andrei I. Onishchenko

We present B_c-meson two-point sum rules at next-to-leading order in NRQCD approximation. Analitycal results for perturbative spectral density and gluon condensate contribution with account for summed Coulomb corrections are given. Estimates of various c-quark masses together with couplings and masses of lowest lying B_c-meson resonances are performed.

Pankaj Jain, Bijoy Kundu, John P. Ralston

The energy dependence of $90^o$ $cm$ fixed angle scattering of $πp \to π&#39; p&#39;$ and $γp\to π^+ n$ at large momentum transfer are found to be well described in terms of interfering short and long distance amplitudes with dynamical phases induced by Sudakov effects. We calculate the color transparency ratio for the corresponding processes in nuclear envi

Farhad Darabi

The model of a relativistic free massive point particle is investigated in the context of a Hamiltonian constraint system. It is shown that de Broglie oscillation, rest mass and inertia may be described within this model of Hamiltonian constraint system.

V. A. De Lorenci, R. Klippert, M. Novello, J. M. Salim

Working on the approximation of low frequency, we present the light cone conditions for a class of theories constructed with the two gauge invariants of the Maxwell field without making use of average over polarization states. Different polarization states are thus identified describing birefringence phenomena. We make an application of the formalism to the

Robert Beig

This paper reviews work, largely due to W. Simon and the author, on multipole theory of static spacetimes. The main purpose is to make this work, which lies at the interface of potential theory, conformal geometry and general relativity, known to mathematicians and to perhaps motivate them to look at the open problems which still remain.

Robert Beig, Bernd G. Schmidt

This article reviews, from a global point of view, rigorous results on time independent spacetimes. Throughout attention is confined to isolated bodies at rest or in uniform rotation in an otherwise empty universe. The discussion starts from first principles and is, as much as possible, self-contained.

Guoying Chee, Yanhua Jia

In terms of Dirac matrices the self-dual and anti-self-dual decomposition of a conformal supergravity is given and a self-dual conformal supergravity theory is developed as a connection dynamic theory in which the basic dynamic variabes include the self-dual spin connection i.e. the Ashtekar connection rather than the triad. The Hamiltonian formulation and t

Yoshinori Cho, Yoshitaka Degura, Kiyoshi Shiraishi

We examine charged static perfect fluid distributions with a dilaton field in the frame-work of general relativity. We consider the case that the Einstein equations reduce to a non-linear version of Poisson equation. We show that Maxwell equation and an equation for a dilaton imply the relation among the charge, mass and dilatonic charge densities.

M. A. Jafarizadeh

Restoration of macroscopic isotropy has been investigated in (d+1)-simplex fractal conductor networks via exact real space renormalization group transformations. Using some theorems of fixed point theory, it has been shown very rigoroursly that the macroscopic conductivity becomes isotropic for large scales and anisotropy vanishes with a scaling exponent whi

S. Schoellmann

A discrete implementation on a lattice of the Active Walker Model is presented. After the model&#39;s validity is shown in simple simulations, more complex simulations of walkers passing consecutively a lattice from an arbitrary starting point at the left border to a random destination on the right border are presented. It is found that walkers may be caught

Hyun-Jae Pi, So-yeon Park, Jysoo Lee, Kyoung J. Lee

Standing wave patterns that arise on the surface of ferrofluids by (single frequency) parametric forcing with an ac magnetic field are investigated experimentally. Depending on the frequency and amplitude of the forcing, the system exhibits various patterns including a superlattice and subharmonic rhombuses as well as conventional harmonic hexagons and subha

A. Tkachenko, O. Terekhov, R. Sunyaev, R. Burenin

We present the results of observations of the soft gamma-ray early afterglows with the energy above 100keV from two bright Gamma-ray bursts detected by the PHEBUS instrument of the GRANAT orbital observatory. We show that the light curves of GRB910402 and GRB920723 events present the afterglow emission with fading fluxes. During our observations ~700s for th

Charles L. Curry

Numerical solutions of the isothermal Lane-Emden equation are presented, corresponding to self-gravitating gaseous cores embedded within a finite density envelope of overall cylindrical symmetry. These structures may be members of a fragmentation hierarchy proceeding from sheets, to filaments, to elongated, prolate clumps. The embedded solutions are the firs

M. Demianski, A. G. Doroshkevich, V. Mueller, V. Turchaninov

The large scale matter distribution in three different simulations of CDM models is investigated and compared with corresponding results of the Zel&#39;dovich theory of nonlinear gravitational instability. We show that the basic characteristics of wall-like structure elements are well described by this theory, and that they can be expressed by the cosmologic

Nataliya a. Zimbovskaya, Joseph L. Birman

We propose a theory for the new maximum recently observed by Willett et al [1] in the longitudinal magnetoresistance of a weakly modulated two-dimensional electron gas (2DEG) near filling factor ν=1/2 for the current driven along the modulation lines. The maximum is superimposed upon a new resonance structure. This occurs due to the geometric resonance of co

Eric G. Blackman, Adam Frank, Carl Welch

MHD winds can emanate from both stars and surrounding accretion disks. It is of interest to know how much wind power is available and which (if either) of the two rotators dominates that power. We investigate this in the context of multi-polar planetary nebulae (PNe) and proto-planetary nebulae (PPNe), for which recent observations have revealed the need for

Mikhail S. Plyushchay

It is shown that the generator of the nonstandard fermion-monopole supersymmetry uncovered by De Jonghe, Macfarlane, Peeters and van Holten, and the generator of its standard N=1/2 supersymmetry have to be supplemented by their product operator to be treated as independent supercharge. As a result, the fermion-monopole system possesses the nonlinear N=3/2 su

Antonella Grassi, Zachary Guralnik, Burt Ovrut

We present explicit methods for computing the discriminant curves and the associated Kodaira type fiber degeneracies of elliptically fibered Calabi-Yau threefolds. These methods are applied to a specific three-family, SU(5) grand unified theory of particle physics within the context of Heterotic M-Theory. It is demonstrated that there is always a region of m

Asantha Cooray

The Sunyaev-Zel&#39;dovich (SZ) effect associated with pressure fluctuations of the large scale structure gas distribution will be probed with current and upcoming wide-field small angular scale cosmic microwave background experiments. We study the generation of pressure fluctuations by baryons which are present in virialized dark matter halos and by baryons

Xinrui Hou

We study the Abrikosov-Nielsen-Olesen string in N=2 supersymmetric QED with N=2-preserving superpotential, in which case the Abrikosov string is found to be 1/2-BPS saturated. Adding a quadratic small perturbation in the superpotential breaks N=2 supersymmetry to N=1 supersymmetry. Then the Abrikosov string is no longer BPS saturated. The difference between

J. Vidal, B. Doucot, R. Mosseri, P. Butaud

We consider two interacting particles evolving in a one-dimensional periodic structure embedded in a magnetic field. We show that the strong localization induced by the magnetic field for particular values of the flux per unit cell is destroyed as soon as the particles interact. We study the spectral and the dynamical aspects of this transition.

Gian Francesco Giudice, Edward W. Kolb, Antonio Riotto

The thermal history of the universe before the epoch of nucleosynthesis is unknown. The maximum temperature in the radiation-dominated era, which we will refer to as the reheat temperature, may have been as low as 0.7 MeV. In this paper we show that a low reheat temperature has important implications for many topics in cosmology. We show that weakly interact

Bohdan Paczynski

A few percent of all stars are variable, yet over 90% of variables brighter than 12 magnitude have not been discovered yet. There is a need for an all sky search and for the early detection of any unexpected events: optical flashes from gamma-ray bursts, novae, dwarf novae, supernovae, `killer asteroids&#39;. The ongoing projects like ROTSE, ASAS, TASS, and

Richard Lieu

Can a simple microscopic model of space and time demonstrate Special Relativity as the macroscopic (aggregate) behavior of an ensemble ? The question will be investigated in three parts. First, it is shown that the Lorentz transformation formally stems from the First Relativity Postulate (FRP) {\it alone} if space-time quantization is a fundamental law of ph

Tobias Baier, Eike Bick, Christof Wetterich

The Hubbard model is reformulated in terms of different ``colored&#39;&#39; fermion species for the electrons or holes at different lattice sites. Antiferromagnetic ordering or d-wave superconductivity can then be described in terms of translationally invariant expectation values for colored composite scalar fields. A suitable mean field approximation for th

Liat Ein-Dor, Richard Metzler, Ido Kanter, Wolfgang Kinzel

The generalization of the problem of adaptive competition, known as the minority game, to the case of $K$ possible choices for each player is addressed, and applied to a system of interacting perceptrons with input and output units of the type of $K$-states Potts-spins. An optimal solution of this minority game as well as the dynamic evolution of the adaptiv

Natxo Alonso-Alberca, Bert Janssen, Pedro J. Silva

We construct a model for dilatonic brane worlds with constant curvature on the brane, i.e. a non-zero four-dimensional cosmological constant, given in function of the dilaton coupling and the cosmological constant of the bulk. We compare this family of solutions to other known dilatonic domain wall solutions and apply a self-tunning mechanism to check the st

A. Jenkins, C. S. Frenk, S. D. M. White, J. M. Colberg

We combine data from a number of N-body simulations to predict the abundance of dark halos in Cold Dark Matter universes over more than 4 orders of magnitude in mass. A comparison of different simulations suggests that the dominant uncertainty in our results is systematic and is smaller than 10--30% at all masses, depending on the halo definition used. In pa