March 1997 arXiv papers — page 2

V. Silveira, I. Waga

We investigate some properties of flat cosmological models with a $Λ$ term that decreases with time as $Λ\propto a^{-m}$ (a is the scale factor and m is a parameter $0\leq m < 3$). The models are equivalent to standard cosmology with matter and radiation plus an exotic fluid with the equation of state $p_x = (m/3 -1)ρ_x$. We study the effect of the decaying

C. Panagiotakopoulos

We construct a hybrid inflationary model associated with the superheavy scale of the minimal supersymmetric standard model which is based on the simplest superpotential for symmetry breaking and in which the inflaton potential along the inflationary trajectory is essentially provided by quasi-canonical supergravity. The resulting spectrum of adiabatic densit

G. J. Gounaris, G. P. Tsirigoti

The possibility of observing CP-violation in the process $γγ\to H$ is investigated for masses of the Higgs particle in the interval $M_z \lsim m_H \lsim 2 m_t$, using a 0.5TeV tunable linear $e^{+} e^{-}$ collider through laser backscattering. The use of polarized beams allows the formation of two different asymmetries sensitive to CP-violating New Physics (

A. P. Dmitriev, I. V. Gornyi, V. Yu. Kachorovskii

We show that the enhancement of backscattering responsible for the weak localization is accompanied by reduction of the scattering in other directions. A simple quasiclassical interpretation of this phenomenon is presented in terms of a small change in the effective differential cross-section for a single impurity. The reduction of the scattering at the arbi

I. A. Batalin, K. Bering, P. H. Damgaard

We consider the description of second-class constraints in a Lagrangian path integral associated with a higher-order $Δ$-operator. Based on two conjugate higher-order $Δ$-operators, we also propose a Lagrangian path integral with $Sp(2)$ symmetry, and describe the corresponding system in the presence of second-class constraints.

Mikolaj Misiak, Stefan Pokorski, Janusz Rosiek

We consider Flavour Changing Neutral Current processes in the framework of the supersymmetric extension of the Standard Model. FCNC constraints on the structure of sfermion mass matrices are reviewed. Furthermore, we analyze supersymmetric contributions to FCNC transitions which remain in the limit of flavour-conserving sfermion mass matrices. Implications o

E. S. Cheb-Terrab, L. G. S. Duarte, L. A. C. P. da Mota

An update of the ODEtools Maple package, for the analytical solving of 1st and 2nd order ODEs using Lie group symmetry methods, is presented. The set of routines includes an ODE-solver and user-level commands realizing most of the relevant steps of the symmetry scheme. The package also includes commands for testing the returned results, and for classifying 1

V. M. Lipunov, K. A. Postnov, M. E. Prokhorov

Assuming binary neutron star mergings as a standard-candle model for GRBs, an independent estimate is obtained for the redshift of GRB970228 and GRB970508 with optical counterparts, using mean statistical properties of GRBs observed by BATSE. We derive z=0.7\pm 0.1 and z=1.9\pm 0.1 for GRB970228 and GRB970508 respectively, depending on the power-law index of

Cai-Dian Lu, Da-Xin Zhang

We analyze the effects of the space-like penguin diagrams in two body B decays $B^-\to K^-{\bar K}^0$ and $B^-\to π^-{\bar K}^0$. Special attention is paid to the operator $Q_6$, whose contribution is large in the BSW model, but vanishes in the PQCD method in the approximation of neglecting the masses in the final states. Suppressions of the space-like pengu

Vitaly Tarasov, Alexander Varchenko

The trigonometric quantized Knizhnik-Zamolodchikov equation (qKZ equation) associated with the quantum group $U_q(sl_2)$ is a system of linear difference equations with values in a tensor product of $U_q(sl_2)$ Verma modules. We solve the equation in terms of multidimensional $q$-hypergeometric functions and define a natural isomorphism between the space of

J. I. Latorre, H. Osborn

The weak energy condition is known to fail in general when applied to expectation values of the the energy momentum tensor in flat space quantum field theory. It is shown how the usual counter arguments against its validity are no longer applicable if the states $|ψ\r$ for which the expectation value is considered are restricted to a suitably defined subspac

Gh. - S. Paraoanu, Horia Scutaru

The Bures distance between two displaced thermal states and the corresponding geometric quantities (statistical metric, volume element, scalar curvature) are computed. Under nonunitary (dissipative) dynamics, the statistical distance shows the same general features previously reported in the literature by Braunstein and Milburn for two--state systems. The sc

Kazuyuki Ochi, Michihiro Hirata, Takashi Takaki

We present a simple model for the $γN \to ππN$ reaction which reproduces the cross sections of the $π^+ π^- p, π^+ π^- n, π^+ π^0 n$ and $π^- π^0 p$ channels over the range of the energies 0.41-0.85 GeV. We use the dynamical model for the resonances, Δ(1232), N^*(1520) and ρ-meson. The total photoabsorption off a nucleon is also discussed.

S. Khoroshkin, D. Lebedev, S. Pakuliak, A. Stolin

The classical limit of the scaled elliptic algebra $A_{\hbar,η}(sl_2)$ is investigated. The limiting Lie algebra is described in two equivalent ways: as a central extension of the algebra of generalized automorphic $sl_2$ valued functions on a strip and as an extended algebra of decreasing automorphic $sl_2$ valued functions on the real line. A bialgebra str

L. A. Dmitrieva, Yu. A. Kuperin, Yu. B. Melnikov

A one-dimensional discrete Stark Hamiltonian with a continuous electric field is constructed by extension theory methods. In absence of the impurities the model is proved to be exactly solvable, the spectrum is shown to be simple, continuous, filling the real axis; the eigenfunctions, the resolvent and the spectral measure are constructed explicitly. For thi

Lorenza Viola, Roberto Onofrio, Tommaso Calarco

The measurement process is introduced in the dynamics of Josephson devices exhibiting quantum behaviour in a macroscopic degree of freedom. The measurement is shown to give rise to a dynamical damping mechanism whose experimental observability could be relevant to understand decoherence in macroscopic quantum systems.

Andrew E. Chubykalo, Stoyan J. Vlaev

We considered the problem of the proportionality of inertial and gravitational masses in classical mechanics. We found that the kinetic energy of a material mass point m in a circular motion with a constant angular velocity around another material point M depends only on its gravitational mass. This fact, together with the known result that the straight line

R. Casalbuoni

The problem of quantizing theories defined over configuration spaces described by non-commuting parameters is considered. In this paper we describe the first step in this direction, that is the definition of an integral over a general algebra.

Z. Ya Turakulov

Variables are separated in Maxwell equations by the Newman-Penrose method of isotropic complex tetrade in the uniformly accelerated spherical coordinate system. Particular solutions are obtained in terms of spin 1 spherical harmonics. PACS: 03.50.De

Valeri V. Dvoeglazov, Myron W. Evans

On the basis of the ordinary mathematical methods we discuss new classes of solutions of the Maxwell&#39;s equations discovered in the papers by D. Ahluwalia, M. Evans and H. M&#39;unera et al.

M. K. Liou, R. Timmermans, B. F. Gibson, Y. Li

The criteria suggested by Welsh and Fearing (nucl-th/9606040) to judge the validity of certain soft-photon amplitudes are examined. We comment on aspects of their analysis which lead to incorrect conclusions about published amplitudes and point out important criteria which were omitted from their analysis.

S. Nishizaki, J. Wambach

Double-dipole excitations in ^{208}Pb are analyzed within a microscopic model explicitly treating 2p2h-excitations. Collective states built from such 2p2h-excitations are shown to appear at about twice the energy of the isovector giant dipole resonance, in agreement with the experimental findings. The calculated cross section for Coulomb excitation at relati

Wolfram Koepf, Dieter Schmersau

Zeilberger&#39;s algorithm provides a method to compute recurrence and differential equations from given hypergeometric series representations, and an adaption of Almquist and Zeilberger computes recurrence and differential equations for hyperexponential integrals. Further versions of this algorithm allow the computation of recurrence and differential equati

Jörg Rambau

Let $P$ and $Q$ be bounded posets. In this note, a lemma is introduced that provides a set of sufficient conditions for the proper part of $P$ being homotopy equivalent to the suspension of the proper part of~$Q$. An application of this lemma is a unified proof of the sphericity of the higher Bruhat orders under both inclusion order (a known proved earlier b

Ennio Gozzi

We review here a path-integral approach to classical mechanics and explore the geometrical meaning of this construction. In particular we bring to light a universal hidden BRS invariance and its geometrical relevance for the Cartan calculus on symplectic manifolds. Together with this BRS invariance we also show the presence of a universal hidden genuine non-

Jonathan Bagger, Ioannis Giannakis

In first-quantized string theory, spacetime symmetries are described by inner automorphisms of the underlying conformal field theory. In this paper we use this approach to illustrate the Higgs effect in string theory. We consider string propagation on M^{24,1} \times S^1, where the circle has radius R, and study SU(2) symmetry breaking as R moves away from i

H. O. Girotti, M. Gomes, J. R. Nascimento, A. J. da Silva

We study the nonrelativistic limit of the theory of a quantum Chern--Simons field minimally coupled to Dirac fermions. To get the nonrelativistic effective Lagrangian one has to incorporate vacuum polarization and anomalous magnetic moment effects. Besides that, an unsuspected quartic fermionic interaction may also be induced. As a by product, the method we

Costas Kounnas

We show the existence of a supersymmetry-breaking mechanism in string theory, where N=4 supersymmetry is broken spontaneously to N=2 and N=1 with moduli-dependent gravitino masses. The BPS spectrum of the theory with lower supersymmetry is in one-to-one correspondence with the spectrum of the heterotic N=4 string. The mass splitting of the N=4 spectrum depen

Nick Evans, Stephen Hsu, Myckola Schwetz

We discuss the introduction of soft breaking terms into the exact solutions of N=1 SQCD using a spurion analysis. The spurion symmetries are not sufficient to determine the behavior of models in which squark or gaugino masses alone are introduced. However, a controlled approximation is obtained in some cases if a supersymmetric mass is first introduced for t

Michael Bershadsky, Vladimir Sadov

We discuss N=2 supersymmetric compactifications to four dimensions from the point of view of F-theory and heterotic theory. In a relatively simple setup, we illustrate the spectral theory for vector bundles on K3xT^2 and discuss the heterotic -- F-theory map. The moduli space of instantons on the 7-brane wrapped around K3 is discussed from the point of view

Yoonbai Kim, Phillial Oh, Chaiho Rim

We consider a uniaxial planar ferromagnet coupled minimally to an Abelian Chern-Simons gauge field and study self-dual solitons which saturate the Bogomol&#39;nyi bound. We find a rich structure of rotationally symmetric static soliton solutions for various uniform background charge densities. For a given ferromagnet material, the properties of these soliton

L. Girlanda, M. Knecht, B. Moussallam, J. Stern

Four of the six parameters defining the two-loop ππscattering amplitude have been determined using Roy dispersion relations. Combining this information with the Standard χPT expressions, we obtain the threshold parameters, low-energy phases and the O(p^4) constants $l_1^r, l_2^r$. The result $l_2^r ( M_ρ ) = ( 1.6 \pm 0.4 \pm 0.9 ) \times 10^{-3} ( {\bar l_2

J. Soffer, O. V. Teryaev

A description of the generalized Gerasimov-Drell-Hearn sum rule for neutron is suggested, using its relation to the Burkhardt-Cottingham sum rule.

J. Kwiecinski, A. D. Martin, A. M. Stasto

We argue that the use of the universal unintegrated gluon distribution and the $k_T$ (or high energy) factorization theorem provides the natural framework for describing observables at small x. We introduce a coupled pair of evolution equations for the unintegrated gluon distribution and the sea quark distribution which incorporate both the resummed leading

Herbi Dreiner, Emanuelle Perez, Yves Sirois

The phenomenology and prospects for a discovery of R-parity violating Supersymmetry at HERA are analysed. Emphasis is put on the direct resonant production of squarks by electron-quark fusion and all possible subsequent decay modes of the squarks are considered. In particular, the full consequences of the mixing in the supersymmetric gaugino-higgsino sector

F. M. L. Almeida, Y. A. Coutinho, J. A. Martins Simões, P. P. Queiroz Filho

We discuss the possibility of same-sign dileptons as a signature for Majorana neutrinos. The production mechanism is given by a single heavy neutrino production and decay proton-proton -> l^{\pm} N X -> l^{\pm} l^{\pm} X&#39;. Cross section and distributions are presented for the LHC energies.

K. H. Kampert, T. C. Awes, P. Stankus, H. H. Gutbrod

In this note we comment on a recent publication in this journal by the CERES (NA45) Collaboration. The authors report to have determined an upper limit on the direct photon yield relative to the decay photon yield in S+Au collisions of 14 % and 7 % by two different methods, respectively. We argue that these limits are unsupported by the results and analysis

Feng Yuan, Cong-Feng Qiao, Kuang-Ta Chao

In this paper, we discuss the prompt j/psi production at e^+e^- colliders via color-singlet and color-octet production mechanisms. The color-singlet production processes include 1) e^+e^- to J/ψgg; 2) e^+e^- to J/ψc\bar{c}; 3) e^+e^- to q \bar q ggJ/ψand e^+e^- to q \bar q gχ_c followed by χ_c to J/ψγ. The color-octet production processes include 1) e^+e^- t

R. David Dikeman, N. G. Uraltsev

We present theoretical predictions for a few phenomenologically interesting distributions in the semileptonic b->u decays which are affected by Fermi motion. The perturbative effects are incorporated at the one-loop level and appear to be very moderate. Our treatment of Fermi motion is based directly on QCD, being encoded in the universal distribution functi

Bo-Qiang Ma

It is shown that the proton spin problem raised by the Ellis-Jaffe sum rule violation does not in conflict with the SU(6) quark model, provided that the relativistic effect from the quark transversal motions, the flavor asymmetry between the $u$ and $d$ valence quarks, and the intrinsic quark-antiquark pairs generated by the non-perturbative meson-baryon flu

Jacek Jezierski

We analyze three classical field theories based on the wave equation: scalar field, electrodynamics and linearized gravity. We derive certain generating formula on a hyperboloid and on a null surface for them. The linearized Einstein equations are analyzed around null infinity. It is shown how the dynamics can be reduced to gauge invariant quanitities in a q

Soumya D. Mohanty

The detection of gravitational waves from coalescing compact binaries would be a computationally intensive process if a single bank of template wave forms (i.e., a one step search) is used. In an earlier paper we had presented a detection strategy, called a two step search}, that utilizes a hierarchy of template banks. It was shown that in the simple case of

Roy Maartens, William Lesame, George Ellis

One of the necessary covariant conditions for gravitational radiation is the vanishing of the divergence of the magnetic Weyl tensor H_{ab}, while H_{ab} itself is nonzero. We complete a recent analysis by showing that in irrotational dust spacetimes, the condition div H=0 evolves consistently in the exact nonlinear theory.

Milan Mijic

A calculation of the one-mode occupation numbers for vacuum fluctuations of massive fields in De Sitter space shows that their use for the generation of classical density perturbations in inflationary cosmology very much depends on their masses and conformal couplings. A new mechanism for the decoherence of relatively massive fields has been identified. A si

C. C. Briggs

A general expression is given for the quartic Lovelock tensor in terms of the Riemann-Christoffel and Ricci curvature tensors and the Riemann curvature scalar for n-dimensional differentiable manifolds having a general linear connection. In addition, expressions are given (in the appendix) for the coefficient of the quartic Lovelock Lagrangian as well as for

W. Kramer, U. Semmelmann, G. Weingart

We consider the Dirac operator on compact quaternionic Kaehler manifolds and prove a lower bound for the spectrum. This estimate is sharp since it is the first eigenvalue of the Dirac operator on the quaternionic projective space.

A. -L. Barabasi, M. A. Makeev, C. S. Lee, R. Cuerno

Recent experimental studies focusing on the morphological properties of surfaces eroded by ion-bombardment report the observation of self-affine fractal surfaces, while others provide evidence about the development of a periodic ripple structure. To explain these discrepancies we derive a stochastic growth equation that describes the evolution of surfaces er

Albert-László Barabási

There is extensive recent experimental evidence of spontaneous superlattice (SL) formation in various II-VI and III-V semiconductors. Here we propose an atomistic mechanism responsible for SL formation, and derive a relation predicting the temperature, flux and miscut dependence of the SL layer thickness. Moreover, the model explains the existence of a criti

N. B. Zhitenev, R. C. Ashoori, L. N. Pfeiffer, K. W. West

We study electron addition spectra of quantum dots in a broad range of electron occupancies starting from the first electron. Spectra for dots containing <200 electrons reveal a surprising feature. Electron additions are not evenly spaced in gate voltage. Rather, they group into bunches. With increasing electron number the bunching evolves from occurring ran

Chris LaSota, Cheng-Zhang Wang, Rici Yu, Henry Krakauer

The lattice instabilities of perovskite structure oxides are responsible for many of their interesting properties, such as temperature-dependent ferroelectric phase transitions. First-principles calculations using linear response theory provide an accurate means to determine the lattice dynamics throughout the entire Brillouin zone (BZ). Using the LAPW linea

O. K. Andersen, S. Y. Savrasov, O. Jepsen, A. I. Liechtenstein

The equilibrium structure, energy bands, phonon dispersions, and s- and d-channel electron-phonon interactions (EPIs) are calculated for the infinite-layer superconductor CaCuO2 doped with 0.24 holes per CuO2. The LDA and the linear-response full-potential LMTO method were used. In the equilibrium structure, oxygen is found to buckle slightly out of the plan

Jurgen Horbach, Walter Kob, Kurt Binder

We present the results of a large scale computer simulation of supercooled silica. We find that at high temperatures the diffusion constants show a non-Arrhenius temperature dependence whereas at low temperature this dependence is also compatible with an Arrhenius law. We demonstrate that at low temperatures the intermediate scattering function shows a two-s

G. Iannaccone, M. Macucci, B. Pellegrini

We present a theory of conductance and noise in generic mesoscopic conductors connected in parallel, and we demonstrate that the additivity of conductance and of shot noise arises as a sole property of the junctions connecting the two (or more) conductors in parallel. Consequences on the functionality of devices based on the Aharonov-Bohm effect are also dra

U. Geppert, H. Rieger, M. Schreckenberg

We present a one dimensional model for diffusion on a hierarchical tree structure. It is shown that this model exhibits aging phenomena although no disorder is present. The origin of aging in this model is therefore the hierarchical structure of phase space.

M. J. Thill

In this paper, I investigate more closely the recently proposed Free Energy Monte Carlo algorithm that is devised in particular for calculations where conventional Monte Carlo simulations struggle with ergodicity problems. The simplest version of the proposed algorithm allows for the determination of the entropy function of statistical systems and/or perform

M. J. Thill

I propose a new algorithm, a free energy Monte Carlo algorithm, for calculations where conventional Monte Carlo simulations struggle with ergodicity problems. The simplest version of the proposed algorithm allows for the determination of the entropy function of statistical systems and/or performs entropy sampling at sufficiently large times. I also mention h

S. Vlaev, D. A. Contreras-Solorio

In the present study we calculate the energy values and the spatial distributions of the bound electronic states in some diffused quantum wells. The calculations are performed within the virtual crystal approximation, $sp^3 s^*$ spin dependent empirical tight-binding model and the surface Green function matching method. A good agreement is found between our

Y. -K. Zhou

The boundary Boltzmann weights are found by solving the boundary star-triangle relations for the Fateev-Zamolodchikov and Kashiwara-Miwa models. We calculate the surface free energies of the models. The critical surface exponent α_s of the Kashiwara-Miwa model is given and satisfies the scaling relation α_b=2α_s-2, where α_b is the bulk exponent.

M. Salaris, S. Cassisi

New theoretical evaluations of the Red Giant Branch Tip (TRGB) luminosity, by adopting the most updated physical inputs in computing canonical stellar models, are presented. Theoretical relations for the run of the TRGB bolometric and I magnitude with the metallicity are provided together with a comparison of the distance scale based on these relations and t

Karl Mannheim

Astrophysical models for the high-energy emission of blazars are reviewed. Blazars ejecting relativistic radio jets at small angles to the line-of-sight are the only type of active galactic nuclei (AGN) discovered above 100 MeV. The gamma-rays apparently originate in the jets which explains the absence of gamma-ray pair creation attenuation. The bulk Lorentz

F. R. Pearce, H. M. P. Couchman

We describe the first parallel implementation of an adaptive particle-particle, particle-mesh code with smoothed particle hydrodynamics. Parallelisation of the serial code, ``Hydra&#39;&#39;, is achieved by using CRAFT, a Cray proprietary language which allows rapid implementation of a serial code on a parallel machine by allowing global addressing of distri

KASCADE Collaboration, K. -H. Kampert

A new extensive air shower (EAS) experiment has been installed at the laboratory site of the Forschungszentrum Karlsruhe. The major goal of the experiment is to determine the chemical composition in the energy range around and above the knee of the primary cosmic ray spectrum. An important advantage of the installation is the capability to simultaneously mea

S. C. Tripathy, H. M. Antia, F. Hill, A. Ambastha

Using the recently obtained GONG frequencies, we investigate the properties of the solar interior by constructing solar models with various input physics like opacities, equation of state, nuclear reaction rates etc. The differential asymptotic inversion technique is then used to infer the relative difference in sound speed between the Sun and solar models.

Paul J. Francis, Bruce E. Woodgate, Anthony C. Danks

We have discovered two new high redshift (z=2.38) galaxies, near the previously known z=2.38 galaxy 2139-4434 B1 (Francis et al. 1996). All three galaxies are strong Ly-alpha emitters, and have much redder continuum colors (I-K about 5) than other optically-selected high redshift galaxies. We hypothesize that these three galaxies are QSO IIs; radio-quiet cou

B. Mathiesen, A. E. Evrard

We examine the likelihoods of different cosmological models and cluster evolutionary histories by comparing semi-analytical predictions of X-ray cluster number counts to observational data from the ROSAT satellite. We model cluster abundance as a function of mass and redshift using a Press-Schechter distribution, and assume the temperature T(M,z) and bolomet

Brian Harbourne

This paper is concerned with determining the number of generators in each degree for minimal sets of homogeneous generators for saturated ideals defining fat point subschemes $Z=m_1p_1+ ... +m_rp_r$ for general sets of points $p_i$ of $P^2$. For thin points (i.e., m_i=1 for all i), a solution is known, in terms of a maximal rank property. Although this prope

Boris V. Karpov

In this paper we deal with algebro-geometrical problems connected with testing S-duality conjecture for super-symmetric Yang-Mills quantum field theories in four dimensions. We describe all field configurations such that beta function coefficient for gauge groups of rank 1 and 2 is zero or negative. We also give special series of such field configurations fo

J. Kalinowski, R. Rueckl, H. Spiesberger, P. M. Zerwas

In supersymmetric theories with R-parity breaking, trilinear couplings of two leptons to scalar sleptons are possible. In electron-positron collisions such interactions would manifest themselves through contact terms in Bhabha scattering and in annihilation to mu or tau pair Interpreting the high x, high Q2 DIS HERA events as charm squark production with squ

David Bowser-Chao, Darwin Chang, Wai-Yee Keung

The leading contributions to the electron (or muon) electric dipole moment due to CP violation in the charged Higgs sector are at the two-loop level. A careful analysis of the model-independent contribution is provided. We also consider specific scenarios to demonstrate how charged Higgs sector CP violation can naturally give rise to large electric dipole mo

M. Barahona, E. Trias, T. P. Orlando, A. E. Duwel

We study the dynamics of fully frustrated, underdamped Josephson arrays. Experiments reveal remarkable similarities among the dc current-voltage characteristics of several kinds of square and triangular arrays, where two resonant voltages are observed. Simulations indicate that a dynamical checkerboard solution underlies these similarities. By assuming such

Gunnar S. Bali, Klaus Schilling, Armin Wachter

For the first time, we determine the complete spin- and momentum-dependent order v^2 corrections to the static interquark potential from simulations of QCD in the valence quark approximation at inverse lattice spacings of 2-3 GeV. A new flavor dependent correction to the central potential is found. We report a 1/r^2 contribution to the long range spin-orbit

Jeong-Hyuck Park

N=1, d=4 superconformal group is studied and its representations are discussed. Under superconformal transformations, left invariant derivatives and some class of superfields, including supercurrents, are shown to follow these representations. In other words, these superfields are quasi-primary by analogy with two dimensional conformal field theory. Based on

P. Butera, M. Comi

High temperature expansions for the free energy, the susceptibility and the second correlation moment of the classical N-vector model [also known as the O(N) symmetric classical spin Heisenberg model or as the lattice O(N) nonlinear sigma model] on the sc and the bcc lattices are extended to order beta^{21} for arbitrary N. The series for the second field de

S. Lukyanov

An integral representation for form-factors of exponential fields in the sine-Gordon model is proposed.

Enrico Carlon, Andrzej Drzewinski

The phase diagram of the 2D Ising model confined between two infinite walls and subject to opposing surface fields and to a bulk &#34;gravitational&#34; field is calculated by means of density matrix renormalization methods. In absence of gravity two phase coexistence is restricted to temperatures below the wetting temperature. We find that gravity restores

Lev Tsimring, Igor Aranson

We propose a phenomenological model for pattern formation in a vertically vibrated layer of granular material. This model exhibits a variety of stable cellular patterns including standing rolls and squares as well as localized objects (oscillons and worms), similar to recent experimental observations(Umbanhowar et al., 1996). The model is an amplitude equati

S. C. Tripathy, Sarbani Basu, J. Christensen-Dalsgaard

We investigate the effect of localized opacity modifications on the sound-speed profile of solar models. The sound-speed difference between the Sun and a solar model is used to deduce the opacity correction that would be required to bring the model into agreement with the Sun. We test this procedure on artificial data for a pair of solar models and apply it

Behzad Bina, Murat Gunaydin

We give a complete classification of the real forms of simple nonlinear superconformal algebras (SCA) and quasi-superconformal algebras (QSCA) and present a unified realization of these algebras with simple symmetry groups. This classification is achieved by establishing a correspondence between simple nonlinear QSCA&#39;s and SCA&#39;s and quaternionic and

Toshiaki Iitaka, Shintaro Nomura, Hideki Hirayama, Xinwei Zhao

An O(N) algorithm is proposed for calculating linear response functions of non-interacting electrons in arbitray potential. This algorithm is based on numerical solution of the time-dependent Schroedinger equation discretized in space, and suitable to parallel- and vector- computation. Since it avoids O(N^3) computational effort of matrix diagonalization, it

M. Alishahiha

A closed form of the Picard-Fuchs equations for N=2 supersymmetric Yang-Mills theories with massless hypermultiplet are obtained for classical Lie gauge groups. We consider any number of massless matter in fundamental representation so as to keep the theory asymptotically free.

Boris Stern, Juri Poutanen, Roland Svensson

Brightness dependent correlations have been conclusively detected in the average time profiles of gamma-ray bursts (GRBs). Determining the time constants of the stretched exponential slopes of the average peak-aligned time profile of GRBs as a function of the peak brightness, we find that the post-peak slope shows time dilation when comparing bright and dim

Howard L. Richards, Naomichi Hatano, M. A. Novotny

By intentionally underestimating the rate of convergence of exact-diagonalization values for the mass or energy gaps of finite systems, we form families of sequences of gap estimates. The gap estimates cross zero with generically nonzero linear terms in their Taylor expansions, so that $ν= 1$ for each member of these sequences of estimates. Thus, the Coheren

Fyodor V. Tkachov

For any near-threshold asymptotic regime and for any Feynman diagram (involving loop and/or phase space integrals), a systematic prescription for explicitly constructing all-logs, all-powers (all-twists) expansions in perfectly factorized form with explicit integrals for coefficients, is presented. The distribution-theoretic nature of the method of asymptoti

Alexander Belopolsky

We present a new geometrical approach to superstrings based on the geometrical theory of integration on supermanifolds. This approach provides an effective way to calculate multi-loop superstring amplitudes for arbitrary backgrounds. It makes possible to calculate amplitudes for the physical states defined as BRST cohomology classes using arbitrary represent

Naohisa Ogawa

Embedding of Klein-Gordon and Dirac particle onto Riemannian submanifold in higher dimensional Minkowski space is given by using Hamiltonian BRST formalism. Up to the ordering and quantum potential term induced by embedding, obtained K-G equation is the usual one in Riemannian space, instead, the obtained Dirac equation is essentially different from the usua

Katsushi Ito

We study the low-energy effective theory of N=2 supersymmetric Yang-Mills theory with the exceptional gauge group $G_{2}$. We obtain the Picard-Fuchs equations for the $G_{2}$ spectral curve and compute multi-instanton contribution to the prepotential. We find that the spectral curve is consistent with the microscopic supersymmetric instanton calculus. It is

F. Lesage, H. Saleur, P. Simonetti

We show that the problem of impurity tunneling in a Luttinger liquid of electrons with spin is solvable in the spin isotropic case ($g_σ=2$, $g_ρ$ arbitrary). The resulting integrable model is similar to a two channel anisotropic Kondo model, but with the impurity spin in a &#34;cyclic representation&#34; of the quantum algebra $su(2)_q$ associated with the

N. J. Cerf, S. E. Koonin

The many-body dynamics of a quantum computer can be reduced to the time evolution of non-interacting quantum bits in auxiliary fields by use of the Hubbard-Stratonovich representation of two-bit quantum gates in terms of one-bit gates. This makes it possible to perform the stochastic simulation of a quantum algorithm, based on the Monte Carlo evaluation of a

Jürgen Audretsch, Michael Mensky

A continuous measurement of energy which is sharp (perfect) leads to the quantum Zeno effect (freezing of the state). Only if the quantum measurement is fuzzy, continuous monitoring gives a readout E(t) from which information about the dynamical development of the state vector of the system may be obtained in certain cases. This is studied in detail. Fuzzine

D. Gurevich, J. Donin, V. Rubstov

Two types of Poisson pencils connected to classical R-matrices and their quantum counterparts are considered. A representation theory of the quantum algebras related to some symmetric orbits in $sl(n)^*$ is constructed. A twisted version of quantum mechanics is discussed.

H. Hofmann, D. Kiderlen

We reconsider the importance of statistical fluctuations for fission dynamics beyond the saddle in the light of recent evaluations of transport coefficients for average motion. The size of these fluctuations are estimated by means of the Kramers-Ingold solution for the inverted oscillator, which allows for an inclusion of quantum effects.

H. Hofmann, D. Kiderlen

We address the dynamics of damped collective modes in terms of first and second moments. The modes are introduced in a self-consistent fashion with the help of a suitable application of linear response theory. Quantum effects in the fluctuations are governed by diffusion coefficients D_{μν}. The latter are obtained through a fluctuation dissipation theorem g

Hiroaki Kouno, Katsuaki Sakamoto, Yoshitaka Iwasaki, Nobuo Noda

Including the vacuum effects, the compressional properties of nuclear matter are studied in the cutoff field theory. Under the Hartree approximation, the low-energy effective Lagrangian is derived in the framework of the renormalization group methods. The coefficients are determined in a way where the physical results hardly depend on the value of the cutoff

G. I. Poulis

The role of relativistic corrections associated with lower Dirac components of the deuteron wavefunction, is examined for parity-violating (PV) electron scattering. The relation between these corrections and negative energy components of the struck nucleon in relativistic PWIA is elucidated. The model dependence induced by describing such effects, using diff

Sergei V. Matveev

We describe theoretical backgrounds for a computer program that recognizes all closed orientable 3-manifolds up to complexity 8. The program can treat also not necessarily closed 3-manifolds of bigger complexities, but here some unrecognizable (by the program) 3-manifolds may occur.

Arun Ram, D. E. Taylor

A general method for computing irreducible representations of Weyl groups and Iwahori-Hecke algebras was introduced earlier by the first author. The representations of the algebras of types $A_n$, $B_n$, $D_n$ and $G_2$ were computed and it is the purpose of this paper to extend these computations to $F_4$. The main goal here is to compute irreducible repres

P. Kanti, N. E. Mavromatos, J. Rizos, K. Tamvakis

We demonstrate linear stability of the dilatonic Black Holes appearing in a string-inspired higher-derivative gravity theory with a Gauss- Bonnet curvature-squared term. The proof is accomplished by mapping the system to a one-dimensional Schrodinger problem which admits no bound states. This result is important in that it constitutes a linearly stable examp

Ivan K. Kostov, Matthias Staudacher, Thomas Wynter

We present a complex matrix gauge model defined on an arbitrary two-dimensional orientable lattice. We rewrite the model&#39;s partition function in terms of a sum over representations of the group U(N). The model solves the general combinatorial problem of counting branched covers of orientable Riemann surfaces with any given, fixed branch point structure.

I. Brevik, R. Sollie

The Casimir energy for the transverse oscillations of a piecewise uniform closed string is calculated. The string consists of 2N pieces of equal length, of alternating type I and type II material, and is taken to be relativistic in the sense that the velocity of sound always equals the velocity of light. By means of a new recursion formula we manage to calcu

Kyoungtae Kimm, Bukyung Sul

We discuss the N=2 supersymmetric extension of the gauged O(3) sigma model in (2+1) dimensions with an abelian Chern-Simons term. It is shown that the self-dual potential and the Bogomolny relations naturally appear as consequences of extended supersymmetry.