July 1996 arXiv papers — page 12

Tsuyoshi Hondou, Yasuji Sawada

In a recent letter [Phys.Rev.Lett. {\bf 30}, 3269 (1995), chao-dyn/9510011], we reported that a macroscopic chaotic determinism emerges in a multistable system: the unidirectional motion of a dissipative particle subject to an apparently symmetric chaotic noise occurs even if the particle is in a spatially symmetric potential. In this paper, we study the glo

J. A. Baldwin, A. Crotts, R. J. Dufour, G. J. Ferland

We reexamine the spectroscopic underpinnings of recent suggestions that [O I] and [Fe II] lines from the Orion H II region are produced in gas where the iron-carrying grains have been destroyed and the electron density is surprisingly high. Our new observations show that previous detections of [O I] 5577 were dominated by telluric emission. Our limits are co

K. Imamura, Y. Sofue

We derive radial and vertical distributions of HI and H2 gas densities in our Galaxy by using the terminal velocity method. We calculate the molecular fraction (f_mol) defined as the ratio of the molecular hydrogen to total hydrogen gas density at galactic longitude l= 33 to 64 deg and galactic latitude b=-2 to +2 deg. The thickness of the molecular dominant

W. J. G. de Blok, S. S. McGaugh

We compare the dynamical properties of two galaxies at identical positions on the Tully-Fisher relation, but with different surface brightnesses. We find that the low surface brightness galaxy UGC 128 has a higher mass-to-light ratio, and yet has lower mass densities than the high surface brightness galaxy NGC 2403. This is true for the gas surface density,

Rajesh Gopakumar, Sunil Mukhi

We study orbifold compactifications of F-theory which lead to $N=1$ supersymmetry in 6 and 4 spacetime dimensions. These are dual to specific orientifolds of M-theory, and in many cases to orientifolds of type IIB string theory. The equivalences are demonstrated by mapping the orbifolding transformations in the F, M and string theories to each other using du

Michele D. Thornley

We present K'(2.1 micron) observations of four nearby flocculent spirals, which clearly show low-level spiral structure and suggest that kiloparsec-scale spiral structure is more prevalent in flocculent spirals than previously supposed. In particular, the prototypical flocculent spiral NGC 5055 is shown to have regular, two-arm spiral structure to a radi

M. A. Vazquez-Mozo

We study the thermodynamics of open superstrings in the presence of $p$-dimensional D-branes. We get some finite temperature dualities relating the one-loop canonical free energy of open strings to the self-energy of D-branes at dual temperature. For the open bosonic string the inverse dual temperature is, as expected, the dual length under T-duality, $4π^{2

Maxim Vybornov

In this paper we present our variant of quantum antisymmetry and quantum Jacobi identity.

V. N. Plechko

We review the applications of the integral over anticommuting Grassmann variables (nonquantum fermionic fields) to the analytic solutions and the field-theoretical formulations for the 2D Ising models. The 2D Ising model partition function $Q$ is presentable as the fermionic Gaussian integral. The use of the spin-polynomial interpretation of the 2D Ising pro

M. Passera, A. Sirlin

The Z^0 resonant amplitude is discussed in general R_ξgauges. When the original on-shell definition of the Z^0 mass M is employed, a gauge dependence of M emerges in the next-to-leading approximation which, although small, is of the same magnitude as the current experimental error. In the following order of expansion, these unphysical effects are unbounded.

H. J. de Vega, I. L. Egusquiza

The string propagation equations in axisymmetric spacetimes are exactly solved by quadratures for a planetoid Ansatz. This is a straight non-oscillating string, radially disposed, which rotates uniformly around the symmetry axis of the spacetime. In Schwarzschild black holes, the string stays outside the horizon pointing towards the origin. In de Sitter spac

Ernest Baver

We build the trigonometric solutions of the Yang-Baxter equation that can not be obtained from quantum groups in any direct way. The solution is obtained using the construction suggested recently from the rational conformal field theory corresponding to the WZW model on $SO(3)_{4 R}=SU(2)_{4 R} / Z_{2}$. We also discuss the full elliptic solution to the Yang

H. B. Gao

We propose a configuration of D-branes welded by analogous orbifold operation to be responsible for the enhancement of $SO(2N)$ gauge symmetry in type II string compactified on the $D_n$-type singular limit of K3. Evidences are discussed from the $D_n$-type ALE and D-manifold point of view. A subtlety regarding the ability of seeing the enhanced $SO(2N)$ gau

Wolfgang Lucha, Franz F. Schöberl

The Hamiltonian of the spinless relativistic Coulomb problem combines the standard Coulomb interaction potential with the square-root operator of relativistic kinematics. This Hamiltonian is known to be bounded from below up to some well-defined critical coupling constant. At this critical coupling constant, however, the differences between all analytically

Seth Major, Lee Smolin

An approach to quantum cosmology, relying on strengths of both canonical and path integral formalisms, is applied to the cosmological model, Bianchi type IX. Physical quantum states are constructed on the maximal slice of the cosmological history. A path integral is derived which evolves observables off the maximal slice. This result is compared a path integ

Sang Pyo Kim, Sung Ku Kim, Kwang-Sup Soh, Jae Hyung Yee

We elaborate the renormalization process of entropy of a nonextremal and an extremal Reissner-Nordström black hole by using the Pauli-Villars regularization method, in which the regulator fields obey either the Bose-Einstein or Fermi-Dirac distribution depending on their spin-statistics. The black hole entropy involves only two renormalization constants. We

Sang Pyo Kim, Sung Ku Kim, Kwang-Sup Soh, Jae Hyung Yee

In order to understand the physical effect of the brick wall boundary condition, we compute the distribution of the zero-point energy of the massless scalar fields minimally coupled to the Schwarzschild and Reissner-Nordström black hole backgrounds. We find that the black hole radiation spectrum depends on the positions of the brick wall and the observer, an

Holger Stark, Tom C. Lubensky

We present a rigorous treatment of the diffusion approximation for multiple light scattering in anisotropic random media, and apply it to director fluctuations in a nematic liquid crystal. For a typical nematic material, 5CB, we give numerical values of the diffusion constants $D_{\|}$ and $D_{\perp}$. We also calculate the temporal autocorrelation function

M. K. Hassan

We discuss the formation of stochastic fractals and multifractals using the kinetic equation of fragmentation approach. We also discuss the potential application of this sequential breaking and attempt to explain how nature creats fractals.

Klaus Kirsten, David J. Toms

We present an analysis of Bose-Einstein condensation for a system of non-interacting spin-0 particles in a harmonic oscillator confining potential trap. We discuss why a confined system of particles differs both qualitatively and quantitatively from an identical system which is not confined. One crucial difference is that a confined system is not characteriz

Claudia Filippi, Xavier Gonze, C. J. Umrigar

In order to assess the accuracy of commonly used approximate exchange-correlation density functionals, we present a comparison of accurate exchange and correlation potentials, exchange energy densities and energy components with the corresponding approximate quantities. Four systems are used as illustrative examples: the model system of two electrons in a ha

Claudia Filippi, C. J. Umrigar, Xavier Gonze

Most approximate exchange-correlation functionals used within density functional theory are constructed as the sum of two distinct contributions for exchange and correlation. Separating the exchange component from the entire functional is useful since, for exchange, exact relations exist under uniform density scaling and spin scaling. In the past, accurate e

Dennis P. Clougherty, Xiang Zhu

We study {{\rm C}$_{60}$} with the use of Thomas-Fermi theory. A spherical shell model is invoked to treat the nuclear potential, where the nuclear and core charges are smeared out into a shell of constant surface charge density. The valence electron distribution and the electrostatic potential are efficiently computed by integration of the Thomas-Fermi equa

R. Klages, J. R. Dorfman

We study diffusion in a one-dimensional periodic array of scatterers modeled by a simple map. The chaotic scattering process for this map can be changed by a control parameter and exhibits the dynamics of a crisis in chaotic scattering. We show that the strong backscattering associated with the crisis mechanism induces a crossover which leads to different as

Sean Keel, James McKernan

We consider the cones of curves and divisors on the moduli space of stable pointed rational curves,M_n, and on the quotient by the symmetric group, Q_n, which is a moduli space of pairs. We find generators for contractible extremal rays of the cone of curves NE_1(M_n), and for the cone of divisors NE^1(Q_n). This second cone turns out to be simplicial. We gi

J. Borlaf, Y. Lozano

We study T-duality for open strings in various $D$-manifolds in the approach of canonical transformations. We show that this approach is particularly useful to study the mapping of the boundary conditions since it provides an explicit relation between initial and dual variables. We consider non-abelian duality transformations and show that under some restric

R. Ansari, M. Aurière, P. Baillon, A. Bouquet

M31 is a very tempting target for a microlensing search of compact objects in galactic haloes. It is the nearest large galaxy, it probably has its own dark halo, and its tilted position with respect to the line of sight provides an unmistakable signature of microlensing. However most stars of M31 are not resolved and one has to use the ``pixel method'&#3

Berndt Müller

Following a recent suggestion by Nielsen, Rugh, and Rugh, we study the energy scaling of the maximal Lyapunov exponent of classical Hamiltonian SU(2) lattice gauge theory. It is shown that the conjectured scaling behavior $λ_0\sim E^{1/4}$ at small energies on the lattice is a finite-time artifact. New numerical results for the maximal Lyapunov exponent are

Joseph Polchinski

The strong coupling limit of a quantum system is in general quite complicated, but in some cases a great simplification occurs: the strongly coupled limit is equivalent to the weakly coupled limit of some other system. In string theory conjectures of this type go back several years, but only in the past year and a half has it been understood to be a general

M. V. Simkin

In previous work on quantum phase transition in granular superconductors, where mean-field theory was used, an assumption was made that the order parameter as a function of the mean field is a convex up function. Though this is not always the case in phase transitions, this assumption must be verified, what is done in this article.

Jan Bartelski, Stanislaw Tatur

We performed a phenomenological fit in order to get quark parton polarized distributions in the nucleon. All data on inclusive and semi-inclusive spin asymmetries measured on nucleon targets were used. We present the results for the flavour dependence of polarized sea inside a nucleon. An excellent agreement between inclusive and semi-inclusive data on polar

J. A. S. Lima, M. Mohazzab

It is argued that when the dimension of space is a constant integer the full set of Einstein's field equations has more information than the spatial components of Einstein's equation plus the energy conservation law. Applying the former approach to the decrumpling FRW cosmology recently proposed, it is shown that the spacetime singularity cannot be a

Felix Ritort

We consider the effects of quantum fluctuations in mean-field quantum spin-glass models with pairwise interactions. We examine the nature of the quantum glass transition at zero temperature in a transverse field. In models (such as the random orthogonal model) where the classical phase transition is discontinuous an analysis using the static approximation re

B. Kramer, D. Belitz, M. Batsch

The problem of non--interacting electrons on a square lattice subject to a random magnetic flux is mapped onto a one--dimensional model with infinitely many orbitals per site. Linking each orbital with $N(\gg1)$ other orbitals maps the problem onto Wegner's $N$-orbital model in the same limit, while the original problem corresponds to $N=1$. The exact so

Maria Morandi Cecchi, Luca Salasnich

In this paper we present some theorems for a class of non--hyperbolic fixed points on ${\bf R}^N$ and then analyze a family of functions $f_θ$ on the plane which have a non--hyperbolic fixed point in the origin. The dynamical properties of the family near the fixed point, like the basin of attraction, are studied. Finally the limits of applicability of the c

Tomasz Plewa, Michal Rozyczka

We discuss some typical problems related to numerical hydrodynamics of a dense interstellar medium. A newly developed hydrodynamical code based on adaptive mesh refinement technique is presented and applied to simulate the evolution of a supernova remnant in a high-density medium. Advantages of this new approach in comparison to commonly used hydrodynamical

O. Bertolami, P. D. Fonseca, P. V. Moniz

The quantum cosmological version of the multidimensional Einstein-Yang-Mills model in a $R \times S^3 \times S^d$ topology is studied in the framework of the Hartle-Hawking proposal. In contrast to previous work in the literature, we consider Yang-Mills field configurations with non-vanishing time-dependent components in both $S^3$ and $S^d$ spaces. We obtai

Emory F Bunn, Andrew R Liddle, Martin White

We supply fitting formulae enabling the normalization of slow-roll inflation models to the four-year COBE data. We fully include the effect of the gravitational wave modes, including the predicted relation of the amplitude of these modes to that of the density perturbations. We provide the normalization of the matter power spectrum, which can be directly use

Andre Kempe, Lauri Karttunen

This paper extends the calculus of regular expressions with new types of replacement expressions that enhance the expressiveness of the simple replace operator defined in Karttunen (1995). Parallel replacement allows multiple replacements to apply simultaneously to the same input without interfering with each other. We also allow a replacement to be constrai

B. Sakita

We first present a general method for extracting collective variables out of non-relativistic fermions by extending the gauge theory of collective coordinates to fermionic systems. We then apply the method to a system of non-interacting flavored fermions confined in a one-dimensional flavor-independent potential. In the limit of a large number of particles w

Gérard Clément, Dmitri Gal'tsov

Stationary four-dimensional BPS solutions to gravity coupled bosonic theories admitting a three-dimensional sigma-model representation on coset spaces are interpreted as null geodesics of the target manifold equipped with a certain number of harmonic maps. For asymptotically flat (or Taub-NUT) space-times such geodesics can be directly parametrized in terms

Andrew Mathas

This paper has been withdrawn because of a gap in the proof of Lemma 3.10. The main reults in this paper have now been proved, and extended in the following papers: S. Ariki and A. Mathas, The number of simple modules of the Hecke algebras of type G(r,1,n) S. Ariki, On the classification of simple modules for cyclotomic Hecke algebras of type G(m,1,n) and Kl

S. V. Zenkin

Considering as an example a simple lattice ansatz for the chiral fermion determinant, we demonstrate that even very mild violation of gauge invariance by the determinant at finite lattice spacing leads to the need for another scale in the full gauge theory. This new scale is much grater than the lattice spacing and is associated with the gauge variables.

A. M. Perelomov

The von Neumann type subsystems of $q$-deformed coherent states are considered. The completeness of such subsystems is proved.

Zahir A. Daya, Stephen W. Morris, John R. de Bruyn

A suspended fluid film with two free surfaces convects when a sufficiently large voltage is applied across it. We present a linear stability analysis for this system. The forces driving convection are due to the interaction of the applied electric field with space charge which develops near the free surfaces. Our analysis is similar to that for the two-dimen

G. Raimann, M. J. Balbes, R. N. Boyd, D. Cano-Ott

Recent network calculations suggest that a high temperature rp-process could explain the abundances of light Mo and Ru isotopes, which have long challenged models of p-process nuclide production. Important ingredients to network calculations involving unstable nuclei near and at the proton drip line are $β$-halflives and decay modes, i.e., whether or not $β$

Georgia Benkart, Chanyoung Lee Shader, Arun Ram

We derive a general result about commuting actions on certain objects in braided rigid monoidal categories. This enables us to define an action of the Brauer algebra on the tensor space $V^{\otimes k}$ which commutes with the action of the orthosymplectic Lie superalgebra $\spo(V)$ and the orthosymplectic Lie color algebra $\spo(V,β)$. We use the Brauer alge

Arun Ram

The purpose of this note is to give an insertion scheme proof of the formula, $$p_μ= \sum_{λ\vdash k} χ^λ(μ)s_λ,\formula$$ where $p_μ$ is the power sum symmetric function, $s_λ$ is the Schur function and $χ^λ(μ)$ is the irreducible character of the symmetric group $S_k$ indexed by the partition $λ$ and evaluated at a permutation of cycle type $μ=(μ_1,\ldots,

Vicente Cortés

For any Lagrangean Kähler submanifold $M \subset T^*{\Bbb C}^n$, there exists a canonical hyper Kähler metric on $T^*M$. A Kähler potential for this metric is given by the generalized Calabi Ansatz of the theoretical physicists Cecotti, Ferrara and Girardello. This correspondence provides a method for the construction of (pseudo) hyper Kähler manifolds with

Alessandra Carbone, S. Semmes

This paper is intended to provide an introduction to cut elimination which is accessible to a broad mathematical audience. Gentzen's cut elimination theorem is not as well known as it deserves to be, and it is tied to a lot of interesting mathematical structure. In particular we try to indicate some dynamical and combinatorial aspects of cut elimination,

Alessandra Carbone, S. Semmes

One often sees a sharp distinction in mathematics between descriptions from the outside and from the inside. Think of defining a set in the plane through an algebraic equation, or dynamically as the closure of the orbit of some point under iterations of a given mapping. In logic one sees this dichotomy in the descriptions of sets of tautologies through seman

A. Polyakov

We propose a hypothesis that all gauge theories are equivalent to a certain non-standard string theory. Different gauge groups are accounted for by weights ascribed to the world sheets of different topologies. The hypothesis is checked in the case of the compact abelian theories, where we show how condensing monopole -instanton fields are reproduced by the s

Ian I. Kogan, Alex Lewis, Oleg A. Soloviev

By using the gauge Ward identities, we study correlation functions of gauged WZNW models. We show that the gauge dressing of the correlation functions can be taken into account as a solution of the Knizhnik-Zamolodchikov equation. Our method is analogous to the analysis of the gravitational dressing of 2D field theories.

G. Delfino, P. Simonetti, J. L. Cardy

It is shown that the scaling operators in the conformal limit of a two-dimensional field theory have massive form factors which obey a simple factorisation property in rapidity space. This has been used to identify such operators within the form factor bootstrap approach. A sum rule which yields the scaling dimension of such operators is also derived.

Jack Wentao Xu

In gauge field theories with asymptotic freedom, the short distance properties of Green's functions can be obtained on the basis of weak coupling perturbation expansions. Within this framework, the large momentum behavior of the structure functions for gluon, quark and ghost propagators is derived. The limits are found for general, covariant, linear gaug

Maurizio Martellini, Mauro Zeni, Francesco Fucito

Yang-Mills theory in the first order formalism appears as the deformation of a topological field theory, the pure BF theory. In this approach new non local observables are inherited from the topological theory and the operators entering the t'Hooft algebra find an explicit realization. A calculation of the {\it vev}'s of these operators is performed

Christian Wieczerkowski, Juri Rolf

We compute the non--trivial infrared $ϕ^4_3$--fixed point by means of an interpolation expansion in fixed dimension. The expansion is formulated for an infinitesimal momentum space renormalization group. We choose a coordinate representation for the fixed point interaction in derivative expansion, and compute its coordinates to high orders by means of comput

Atish Dabholkar, Jaemo Park

An orientifold of Type-IIB theory on a $K3$ realized as a $Z_2$ orbifold is constructed which corresponds to F-theory compactification on a Calabi-Yau orbifold with Hodge numbers $(51, 3)$. The T-dual of this model is analogous to an orbifold with discrete torsion in that the action of orientation reversal has an additional phase on the twisted sectors, and

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

We investigate the indications of flavor oscillations that come from the anomalous flavor composition of the atmospheric neutrino flux observed in some underground experiments. We study the information coming from the neutrino-induced $μ$-like and $e$-like events both in the sub-GeV energy range (Kamiokande, IMB, Fr{é}jus, and NUSEX experiments) and in the m

C. D. Froggatt, H. B. Nielsen, D. J. Smith

We present an extension of the Standard Model (SM) without supersymmetry, which we use to calculate order of magnitude values for the elements of the mass matrices in the SM. In our model we can fit the 9 quark and lepton masses and 3 mixing angles using only 3 free parameters, with the overall mass scale set by the electroweak interaction. The specific mode

N. Ferrari, G. Fiorentini, B. Ricci

Exposure to a $^{51}$Cr neutrino source as that used in Gallex will provide an excellent overall performance test of Borexino, which should collect about 1400 source induced events, with an initial rate of about 35 counts per day. This will be particularly important if MSW-small-angle turns out to be the solution of the solar neutrino problem. In addition, i

N. V. Krasnikov, A. A. Pivovarov

We argue that accounting for higher order corrections in QCD by integrating a running coupling constant through an infrared region can be most easily done with making use of a scheme without the Landau pole. Within this approach the entire ambiguity of the answer is identical to that of the choice of renormalization scheme. The uncertainties for the $τ$ lept

S. Kumano, M. Miyama

Q**2 dependence of nuclear structure functions is important for understanding perturbative QCD in nuclear environment. However, current experimental data are not sufficient for studying nuclear dependence in the Q**2 evolution because the data are limited in the small Q**2 region at small x. The future HERA program can study the evolution in the large Q**2 r

V. Bernard, N. Kaiser, Ulf-G. Meißner

We calculate the one--loop contributions of order $M_π^4$ to the difference $Δ_R$ between the on--shell pion--nucleon scattering amplitude $\bar{D}^+(0,2M_π^2)$ at the Cheng--Dashen point $ν=0$, $t=2M_π^2$ and the scalar form factor $σ(2M_π^2)$ in the framework of heavy baryon chiral perturbation theory. We proof that to this order $Δ_R$ contains $no$ chiral

Stefano Capitani

We present the computation, in lattice QCD, of the renormalization constants and mixing coefficients of operators that measure the first two moments of DIS Structure Functions. These calculations have been performed using the Sheikholeslami-Wohlert O(a) improved ``clover'' action, which is known to reduce the systematic error associated with the fini

V. Gimenez, G. Martinelli, C. T. Sachrajda

We present a high statistics lattice calculation of the B--meson binding energy $\overlineΛ$ of the heavy--quark inside the pseudoscalar B--meson. Our numerical results have been obtained from several independent numerical simulations at $β=6.0$, $6.2$ and $6.4$, and using, for the meson correlators, the results obtained by the APE group at the same values o

R. B. Mann, T. Ohta

We present an exact solution to the problem of the relativistic motion of 2 point masses in $(1+1)$ dimensional dilaton gravity. The motion of the bodies is governed entirely by their mutual gravitational influence, and the spacetime metric is likewise fully determined by their stress-energy. A Newtonian limit exists, and there is a static gravitational pote

Cayetano Di Bartolo

The Gauss constraint in the extended loop representation for quantum gravity is studied. It is shown that there exists a sector of the state space that is rigorously gauge invariant without the generic convergence issues of the extended holonomies.

N. Kumar, A. M. Jayannavar

The Thouless formula \(G = (e^2/h)(E_c/Δ)\) for the two-probe dc conductance $G$ of a d-dimensional mesoscopic cube is re-analysed to relate its quantum capacitance $C_Q$ to the reciprocal of the level spacing $Δ$. To this end, the escape time-scale $τ$ occurring in the Thouless correlation energy \(E_c = \hbar/τ\) is interpreted as the {\em time constant} \

You-Quan Li, Zhong-Shui Ma

The quantum-mechanical problem of a many-particle system with a single impurity in one-dimension, interacting by a delta-function, is solved. The wave-function for a bosonic system and the related secular equation for the spectrum are obtained. The energy per length is calculated in the thermodynamic limit.

M. Schroeder, W. Kinzel, I. Kanter

A perceptron is trained by a random bit sequence. In comparison to the corresponding classification problem, the storage capacity decreases to alpha_c=1.70\pm 0.02 due to correlations between input and output bits. The numerical results are supported by a signal to noise analysis of Hebbian weights.

I. Pagonabarraga, P. Wojtaszczyk, J. M. Rubi, B. Senger

The ballistic deposition of particles by taking hydrodynamic interactions (HI) into account has been studied by means of computer simulations. The radial distribution function of the assembly of particles deposited on a plane has been determined as a function of the coverage and compared to experimental data. It appears that the introduction of HI in the mod

Madan Rao, Surajit Sengupta

We derive a coarse grained, free-energy functional which describes droplet configurations arising on nucleation of a product crystal within a parent. This involves a new `slow' vacancy mode that lives at the parent-product interface. A mode-coupling theory suggests that a {\it slow} quench from the parent phase produces an equilibrium product, while a {\

T. Obermeier, T. Pruschke, J. Keller

Recent experiments on the Fermi surface and the electronic structure of the cuprate-supercondutors showed the importance of short range antiferromagnetic correlations for the physics in these systems. Theoretically, features like shadow bands were predicted and calculated mainly for the Hubbard model. In our approach we calculate an approximate selfenergy of

J. A. Melsen, P. W. Brouwer, K. M. Frahm, C. W. J. Beenakker

We explore the effects of the proximity to a superconductor on the level density of a billiard for the two extreme cases that the classical motion in the billiard is chaotic or integrable. In zero magnetic field and for a uniform phase in the superconductor, a chaotic billiard has an excitation gap equal to the Thouless energy. In contrast, an integrable (re

V. V. Flambaum, F. M. Izrailev, G. Casati

The model of Fermi particles with random two-body interaction is investigated. This model allows to study the origin and accuracy of statistical laws in few-body systems, the role of interaction and chaos in thermalization, Fermi-Dirac distribution for quasi-particles with spreading widths, matrix elements of external field and enhancement of weak perturbati

Th. Pruschke, Th. Obermeier, J. Keller

We present results for the {\em dynamical}\/ magnetic susceptibility of the $t$-$J$ model, calculated with the dynamical mean field theory. For $J=0$ we find enhanced ferromagnetic correlations but an otherwise relatively $\vec{q}$-independent dynamical magnetic susceptibility. For $J>0$ the explicit antiferromagnetic exchange leads to a dynamic spin structu

David L. O'Brien, Paul A. Pearce

The surface free energies, interfacial tensions and correlation lengths of the Andrews-Baxter-Forrester models in regimes III and IV are calculated with fixed boundary conditions. The interfacial tensions are calculated between arbitrary phases and are shown to be additive. The associated critical exponents are given by $2-α_s=μ=ν$ with $ν=(L+1)/4$ in regime

Almut Beige, Gerhard C. Hegerfeldt

It has been proposed by Cook (Phys. Scr. T 21, 49 (1988)) to use a short probe laser pulse for state measurements of two-level systems. In previous work we have investigated to what extent this proposal fulfills the projection postulate if ideal photon detectors are considered. For detectors with overall efficiency less than 1 complications arise for single

F. W. Stecker

High energy gamma-rays and neutrinos can be produced both by the annihilation and by the possible slow decay of dark matter particles. We discuss the fluxes and spectra of such secondaries produced by dark matter particles in the universe and their observability in competition with other astrophysical gamma-ray signals and with atmospheric neutrinos. To do t

Domingos Barbosa, James G. Bartlett, Alain Blanchard, Jamila Oukbir

We examine how the Sunyaev-Zel'dovich (SZ) effect of clusters can probe $Ω_{o}$. Using self-consistent models of X-ray clusters in the context of hierarchical models of structure formation, we show that both the mean Compton {\it y} parameter and the number of clusters observed via the SZ effect strongly depend on $Ω_{o}$. These quantities are higher in

Frank C. van den Bosch, P. Tim de Zeeuw

Recently, observations with the Hubble Space Telescope have revealed small stellar discs embedded in the nuclei of a number of ellipticals and S0s. In this paper we construct two-integral axisymmetric models for such systems. We calculate the even part of the phase-space distribution function, and specify the odd part by means of a simple parameterization. W

R. Pain, I. M. Hook, S. Deustua, S. Gabi

We present the first measurement of the rate of Type Ia supernovae at high redshift. The result is derived using a large subset of data from the Supernova Cosmology Project. Three supernovae were discovered in a surveyed area of 1.7 square degrees. The survey spanned a $\sim 3$ week baseline and used images with $3σ$ limiting magnitude of $R\sim 23$. We pres

I. N. Reid, Lin Yan, S. Majewski, I. Thompson

We have combined deep starcount data with Galaxy model predictions to investigate how effectively such measurements probe the faint end of the halo luminosity function. We have tested a number of star/galaxy classification techniques using images taken in 0.5 arcsecond seeing with LRIS on the Keck telescope, and we find that different combinations of these t

J. C. Niemeyer, S. E. Woosley

The flame born in the deep interior of a white dwarf that becomes a Type Ia supernova is subject to several instabilities. We briefly review these instabilities and the corresponding flame acceleration. We discuss the conditions necessary for each of the currently proposed explosion mechanisms and the attendant uncertainties. A grid of critical masses for de

Paolo Casati, Gregorio Falqui, Franco Magri, Marco Pedroni

We introduce a hierarchy of mutually commuting dynamical systems on a finite number of Laurent series. This hierarchy can be seen as a prolongation of the KP hierarchy, or a ``reduction'' in which the space coordinate is identified with an arbitrarily chosen time of a bigger dynamical system. Fractional KdV hierarchies are gotten by means of further

Vladimir Baranovsky, Victor Ginzburg

We added an additional result (theorem 1.6) that strengthenns our main theorem in the G=GL-case by establishing an equivalence of tensor categories.

T. T. S. Kuo, F. Krmpotic, Y. Tzeng

We present a microscopic study of halo nuclei, starting from the Paris and Bonn potentials and employing a two-frequency shell model approach. It is found that the core-polarization effect is dramatically suppressed in such nuclei. Consequently the effective interaction for halo nucleons is almost entirely given by the bare G-matrix alone, which presently ca

Piero Olla

The behavior of a spheroidal vesicle, in a plane shear flow bounded from one side by a wall, is analysed when the distance from the wall is much larger than the spheroid radius. It is found that tank treading motions produce a transverse drift away from the wall, proportional to the spheroid eccentricity and the inverse square of the distance from the wall.

Efrat Shimshoni, Assa Auerbach

We model the insulator neighboring the 1/k quantum Hall phase by a random network of puddles of filling fraction 1/k. The puddles are coupled by weak tunnel barriers. Using Kirchoff's laws we prove that the macroscopic Hall resistivity is quantized at $k h/ e^2$ and independent of magnetic field and current bias -- in agreement with recent experimental o

A. I. Bochkarev, R. S. Willey

We study electroweak parameters sensitive to the radiative corrections, such as $ρ$-ratio and $\hff$ decay rates in the $\ms$-scheme in the heavy $t$-quark mass limit $m_{t} \gg m_{w}$. In $\ms$-scheme the two-loop electroweak corrections $\sim m_{t}^{4}$ dominate over the QCD corrections $\sim \as m_{t}^{2}$ in the $ρ$-ratio. The relation between the on-she

G. Dethloff, S. Orevkov, M. Zaidenberg

Let $C \s \pr^2$ be an irreducible plane curve whose dual $C^* \s \pr^{2*}$ is an immersed curve which is neither a conic nor a nodal cubic. The main result states that the Poincaré group $π_1(\pr^2 \se C)$ contains a free group with two generators. If the geometric genus $g$ of $C$ is at least 2, then a subgroup of $G$ can be mapped epimorphically onto the

Luca Zampieri, John C. Miller, Roberto Turolla

Results are presented from a time--dependent, numerical investigation of spherical accretion onto black holes, within the framework of relativistic radiation hydrodynamics. We have studied the stability of self--consistent, stationary solutions of black hole accretion with respect to thermal and radiative perturbations and also the non--linear evolution of u

Takashi Hara, Tatsuhiko Koike, Satoshi Adachi

We present a general framework for understanding and analyzing critical behaviour in gravitational collapse. We adopt the method of renormalization group, which has the following advantages. (1) It provides a natural explanation for various types of universality and scaling observed in numerical studies. In particular, universality in initial data space and

F. Schwabl, U. C. Täuber

We review the theory of second--order (ferro--)elastic phase transitions, where the order parameter consists of a certain linear combination of strain tensor components, and the accompanying soft mode is an acoustic phonon. In three--dimensional crystals, the softening can occur in one-- or two--dimensional soft sectors. The ensuing anisotropy reduces the ef

Seungwon Baek, P. Ko, Jungil Lee, H. S. Song

We consider the energy and the polar angle distributions of J/ψ's produced via the color-singlet and the color-octet (^3S_1^{(8)}) mechanisms in Z^0 \to J/ψ+X at LEP. Since both distributions of the J/ψproduced via color-octet mechanism are significantly different from those via color-singlet mechanism, these observables can be used as tests of color-oct

Richard Hain, Eduard Looijenga

This is a survey paper that also contains some new results. It will appear in the proceedings of the AMS summer research institute on Algebraic Geometry at Santa Cruz.

Mordehai Milgrom

We add to the lore of spherical, stellar-system models a two-parameter family with an anisotropic velocity dispersion, and a central point mass (``black hole''). The ratio of the tangential to radial dispersions, is constant--and constitutes the first parameter--while each decreases with radius as r^{-1/2}. The second parameter is the ratio of the ce

V. D. Dzhunushaliev

The multidimensional gravity on principal bundle with structural SU(2) gauge group is considered. The Lorentzian wormhole solution disposed between two null surfaces is founded in this case. As the nondiagonal components are similar to a gauge fields (in Kaluza - Klein's sense) then in some sense this solution is dual to the black hole in 4D Einstein - Y

J. Hisano, K. Tobe, T. Yanagida

We point out that if the Peccei-Quinn symmetry breaking scale $F_a$ is in a range of the hadronic axion window ($F_a\sim 10^6$GeV), the ee$γγ+/\!\!\!\! E_T$ event in the CDF experiment can be naturally explained by a no-scale supergravity model with a light axino. We also stress that the hadronic axion window still survives the intergalactic photon search, s