March 1998 arXiv papers — page 12

Matias Zaldarriaga, Uros Seljak

We investigate the effect of gravitational lensing by matter distribution in the universe on the cosmic microwave background (CMB) polarization power spectra and temperature-polarization cross-correlation spectrum. As in the case of temperature spectrum gravitational lensing leads to smoothing of narrow features and enhancement of power on the damping tail o

David L. Shupe, Fan Fang, Perry B. Hacking, John P. Huchra

The local luminosity function at 25 $μ$m provides the basis for interpreting the results of deep mid-infrared surveys planned or in progress with space astrophysics missions including ISO, WIRE and SIRTF. We have selected a sample of 1458 galaxies from the IRAS Faint Source Survey with a flux density limit of 250 mJy at 25 $μ$m. The local luminosity function

A. Udalski, M. Szymanski, M. Kubiak, G. Pietrzynski

We present a new distance determination to the Large and Small Magellanic Clouds using the newly developed red clump stars method (Paczynski and Stanek 1998). This new, single-step, Hipparcos calibrated method seems to be one of the most precise techniques of distance determination with very small statistical error due to large number of red clump stars usua

Marco Lombardi, Giuseppe Bertin

In this paper we provide a statistical analysis of the parameter-free method often used in weak lensing mass reconstructions. It is found that a proper assessment of the errors involved in such a non-local analysis requires the study of the relevant two-point correlation functions. After calculating the two-point correlation function for the reduced shear, w

Ori Ganor, Lubos Motl

We study non-linear corrections to the low-energy description of the (2,0) theory. We argue for the existence of a topological correction term similar to the C3 wedge X8(R) in M-theory. This term can be traced to a classical effect in supergravity and to a one-loop diagram of the effective 4+1D Super Yang-Mills. We study other terms which are related to it b

J. Oscar Rosas-Ortiz

By applying algebraic techniques, we construct a two-parametric family of strictly isospectral Hydrogen-like potentials as well as some of its one-parametric limits. An additional one-parametric almost isospectral family of Hydrogen-like potentials is also investigated. It is argued that the construction of a SUSY partner Hamiltonian using a factorization en

S. Deser, M. Henneaux, A. Schwimmer

We present two novel derivations of the recently established $(-)^p$ factor in the charge quantization condition for $p$-brane dyon sources in spacetime dimension $D$=$2p$+2. The first requires consistency of the condition under the charge shifts produced by (generalized) $θ$-terms. The second traces the sign difference between adjoining dimensions to compac

Lawrence R. Pratt, Randall A. LaViolette

It is shown how traditional development of theories of fluids based upon the concept of physical clustering can be adapted to an alternative local clustering definition. The alternative definition can preserve a detailed valence description of the interactions between a solution species and its near-neighbors, i.e., cooperativity and saturation of coordinati

Qimiao Si

We study the effect of spin injection into a Luttinger liquid. The spin-injection-detection setup of Johnson and Silsbee is considered; here spins injected into the Luttinger liquid induce, across an interface with a ferromagnetic metal, either a spin-dependent current ($I_s$) or a spin-dependent boundary voltage ($V_s$). We find that the spin-charge separat

R. K. Bhaduri, N. D. Whelan, M. Brack, H. G. Miller

Periodic orbit expressions for the density of states lead to spurious results when directly used to calculate quantities of thermodynamic interest. This is because the trace formula is usually valid only for large energies while the calculations make use of it at all energies. We present a prescription for circumventing this problem by isolating contribution

E. Balkovsky, V. Lebedev

We consider high-order correlation functions of the passive scalar in the Kraichnan model. Using the instanton formalism we find the scaling exponents $ζ_n$ of the structure functions $S_n$ for $n\gg1$ under the additional condition $dζ_2\gg1$ (where $d$ is the dimensionality of space). At $n<n_c$ (where $n_c = dζ_2/[2(2-ζ_2)]$) the exponents are $ζ_n=(ζ_2/4

John F. Donoghue, Fabrizio Gabbiani

We have previously analysed the chiral predictions for the decay K_L -> pi0 gamma e+ e- and discussed how experimental measurements of this process can help our understanding of chiral theories and of CP tests. Motivated by the possibility that the analogous muonic process may soon be measurable, we extend this calculation to the decay K_L -> pi0 gamma mu+ m

Daniel M. Danchev

The three dimensional mean spherical model on a hypercubic lattice with a film geometry $L\times \infty ^2$ under periodic boundary conditions is considered in the presence of an external magnetic field $H$. The universal Casimir amplitude $Δ$ and the Binder&#39;s cumulant ratio $B$ are calculated exactly and found to be $Δ=-2ζ(3)/(5π)\approx -0.153051$ and

N. Itzhaki, A. A. Tseytlin, S. Yankielowicz

We construct supergravity solutions describing branes (D2-branes or NS5-branes or waves) localized within D6-branes in the region close to the core of the D6-branes. Other similar string-theory and M-theory `near-core&#39; localized solutions can be found by applying U-duality and/or lifting D=10 solutions to D=11. In particular, the D2-branes localized on D

L. Pozzetti, P. Madau, G. Zamorani, H. C. Ferguson

We discuss the deep galaxy counts from the Hubble Deep Field (HDF) imaging survey. At faint magnitudes, the slope of the differential number-magnitude relation is flatter than 0.2 in all four HDF bandpasses. In the ultraviolet, a fluctuation analysis shows that the flattening observed below U=26 mag is not due to incompleteness and is more pronounced than in

G. Feverati, F. Ravanini, G. Takacs

We develop Truncated Conformal Space (TCS) technique for perturbations of c=1 Conformal Field Theories. We use it to give the first numerical evidence of the validity of the non-linear integral equation (NLIE) derived from light-cone lattice regularization at intermediate scales. A controversy on the quantization of Bethe states is solved by this numerical c

V. B. Derjagin, A. N. Leznov, A. Sorin

The general solution of the two-dimensional integrable generalization of the f-Toda chain with fixed ends is explicitly presented in terms of matrix elements of various fundamental representations of the SL(n|n-1) supergroup. The dominant role of the representation theory of graded Lie algebras in the problem of constructing integrable mappings and lattices

Stefan Kehrein

The zero temperature Mott-Hubbard transition as a function of the Coulomb repulsion U is investigated in the limit of large dimensions. The behavior of the density of states near the transition at U=U_c is analyzed in all orders of the skeleton expansion. It is shown that only two transition scenarios are consistent with the skeleton expansion for U<U_c: (i)

Stan Bentvelsen, Irmtraud Meyer

Jet clustering algorithms are widely used to analyse hadronic events in high energy collisions. Recently a new clustering method, known as `Cambridge&#39;, has been introduced. In this article we present an algorithm to determine the transition values of y_cut for this clustering scheme, which allows to resolve any event to a definite number of jets in the f

Eri Asakawa, Jun-ichi Kamoshita, Akio Sugamoto

We examine the stop production scenario for the anomalous excess of high $Q^2$ events observed at HERA, by taking into account the constraints coming from the leptoquark search at Tevatron and the atomic parity violation experiments. This scenario is shown to survive persistently even under the severe constraints from the other experiments. In the analysis,

Holger Frahm, Markus P. Pfannmüller, A. M. Tsvelik

An exactly soluble model describing a spin S=1 antiferromagnetic chain doped with mobile S=1/2 carriers is constructed. In its continuum limit the undoped state is described by three gapless Majorana fermions composing the SU(2) triplet. Doping adds to this a scalar charge field and a singlet Majorana fermion with different velocity. We argue that this mode

Z. F. Ezawa

We propose an improved composite-boson theory of quantum Hall ferromagnets, where the field operator describes solely the physical degrees of freedom representing the deviation from the ground state. In this scheme skyrmions appear merely as generic excitations confined in the lowest Landau level. We evaluate the excitation energy of one skyrmion. Our theore

G. Misguich, B. Bernu, C. Lhuillier, C. Waldtmann

Using exact diagonalizations, we investigate the T=0 phase diagram of the Multi-Spin Exchange (MSE) model on the triangular lattice: we find a transition separating a ferromagnetic phase from a non-magnetic gapped Spin Liquid phase. Systems far enough from the ferromagnetic transition have a metamagnetic behavior with magnetization plateaus at m/m_sat=0 and

Valery P. Gusynin, Vadim M. Loktev, Rachel M. Quick, Sergei G. Sharapov

A phase diagram for a 2D metal with variable carrier density has been studied using the modulus-phase representation for the order parameter in a fully microscopic treatment. This amounts to splitting the degrees of freedom into neutral fermion and charged boson degrees of freedom. Although true long range order is forbidden in two dimensions, long range ord

A. V. Radyushkin

We argue that at moderately large momentum transfer -t <10 GeV^2, hadronic form factors and wide-angle Compton scattering amplitudes are dominated by mechanism corresponding to overlap of soft wave functions. We show that the soft contribution in both cases can be described in terms of the same universal nonforward parton densities (ND&#39;s) F(x;t), which a

W. A. Rodrigues, Jayme Vaz, Erasmo Recami

In this note we generalized the Dirac non-linear electrodynamics, by introducing two potentials (namely, the vector potential A and the pseudo-vector potential gamma^5 B of the electromagnetic theory with charges and magnetic monopoles) and by imposing the pseudoscalar part of the product omega.omega* to be zero, with omega = A + gamma^5 B. We show that the

Vladimir S. Mashkevich

We argue that the claim given in quant-ph/9801014 remains untenable in the revised version. The fallacy in the proof is a misinterpretation of the no-cloning and teleportation theorems, which do not involve time and reference frames.

Frank Gaitan

The generic Berry phase scenario in which a two-level system is coupled to a second system whose dynamical coordinate is slowly-varying is generalized to allow for stochastic evolution of the slow system. The stochastic behavior is produced by coupling the slow system to a heat resevoir which is modeled by a bath of harmonic oscillators initially in equilibr

Harry Buhrman, Richard Cleve, Avi Wigderson

We present a simple and general simulation technique that transforms any black-box quantum algorithm (a la Grover&#39;s database search algorithm) to a quantum communication protocol for a related problem, in a way that fully exploits the quantum parallelism. This allows us to obtain new positive and negative results. The positive results are novel quantum c

M. Begemann-Blaich, ALADIN collaboration

Momenta and masses of heavy projectile fragments (Z >= 8), produced in collisions of 197Au with C, Al, Cu and Pb targets at E/A = 600 MeV, were determined with the ALADIN magnetic spectrometer at SIS. An analysis of kinematic correlations between the two and three heaviest projectile fragments in their rest frame was performed. The sensitivity of these corre

Georgia Benkart, Tom Roby

The algebra generated by the down and up operators on a differential partially ordered set (poset) encodes essential enumerative and structural properties of the poset. Motivated by the algebras generated by the down and up operators on posets, we introduce here a family of infinite-dimensional associative algebras called down-up algebras. We show that down-

Bernard Shiffman, Steve Zelditch

We study the limit distribution of zeros of certain sequences of holomorphic sections of high powers $L^N$ of a positive holomorphic Hermitian line bundle $L$ over a compact complex manifold $M$. Our first result concerns `random&#39; sequences of sections. Using the natural probability measure on the space of sequences of orthonormal bases $\{S^N_j\}$ of $H

Matilde Marcolli, Varghese Mathai

The twisted Connes-Moscovici higher index theorem is generalized to the case of good orbifolds. The higher index is shown to be a rational number, and in fact non-integer in specific examples of 2-orbifolds. This results in a non-commutative geometry model that predicts the occurrence of fractional quantum numbers in the Hall effect on the hyperbolic plane.

Ralf Hinterding, Julius Wess

The q-special functions appear naturally in q-deformed quantum mechanics and both sides profit from this fact. Here we study the relation between the q-deformed harmonic oscillator and the q-Hermite polynomials. We discuss: recursion formula, generating function, Christoffel-Darboux identity, orthogonality relations and the moment functional.

P. J. Fitzsimmons

Let X and Y be time-homogeneous Markov processes with common state space E, and assume that the transition kernels of X and Y admit densities with respect to suitable reference measures. We show that if there is a time t>0 such that, for each x\in E, the conditional distribution of (X_s)_{0 < s < t}, given X_0 = x = X_t, coincides with the conditional distri

J. Denef, F. Loeser

We introduce motivic analogues of p-adic exponential integrals. We prove a basic multiplicativity property from which we deduce a motivic analogue of the Thom-Sebastiani Theorem. In particular, we obtain a new proof of the Thom-Sebastiani Theorem for the Hodge spectrum of (non isolated) singularities of functions.

Hao Chen, Shihoko Ishii

In this paper we show the lower bound of the set of non-zero $-K^2$ for normal surface singularities establishing that this set has no accumulation points from above. We also prove that every accumulation point from below is a rational number and every positive integer is an accumulation point. Every rational number can be an accumulation point modulo $\bZ$.

S. Ferrara, A. Kehagias, H. Partouche, A. Zaffaroni

We consider superconformal field theories in three and six dimensions with eight supercharges which can be realized on the world-volume of M-theory branes sitting at orbifold singularities. We find that they should admit a N=4 and N=2 supergravity dual in AdS_4 and AdS_7, respectively. We discuss the characteristics of the corresponding gauged supergravities

Erich Poppitz, Sandip P. Trivedi

Dynamical supersymmetry breaking is a fascinating theoretical problem. It is also of phenomenological significance. A better understanding of this phenomenon can help in model building, which in turn is useful in guiding the search for supersymmetry. In this article, we review the recent developments in the field. We discuss a few examples, which allow us to

V. V. Nesterenko, I. G. Pirozhenko

The Casimir energy of a solid ball (or cavity in an infinite medium) is calculated by a direct frequency summation using the contour integration. The dispersion is taken into account, and the divergences are removed by making use of the zeta function technique. The Casimir energy of a dielectric ball (or cavity) turns out to be positive, it being increased w

Victor A. Matveev, Grigorii B. Pivovarov

Local effective action is derived to describe Regge asymptotic of Yang-Mills theories. Local symmetries of the effective action originating from the gauge symmetry of the underlying Yang-Mills theory are studied. Multicomponent effective action is introduced to express the symmetry transformations as field transformations. The algebra of these symmetries is

Krzysztof Gawedzki, Pascal Tran-Ngoc-Bich

The paper gives a quick account of the simplest cases of the Hitchin integrable systems and of the Knizhnik-Zamolodchikov-Bernard connection at genus 0, 1 and 2. In particular, we construct the action-angle variables of the genus 2 Hitchin system with group SL(2) by exploiting its relation to the classical Neumann integrable systems.

Dariusz Chruscinski

In the previous paper (hep-th/9712161) it was shown that the nonlinear Born-Infeld field equations supplemented by the &#34;dynamical condition&#34; (certain boundary condition for the field along the particle&#39;s trajectory) define perfectly deterministic theory, i.e. particle&#39;s trajectory is determined without any equations of motion. In the present

Steven Weinberg

A perturbative non-renormalization theorem is presented that applies to general supersymmetric theories, including non-renormalizable theories in which the $\int d^2θ$ integrand is an arbitrary gauge-invariant function $F(Φ,W)$ of the chiral superfields $Φ$ and gauge field-strength superfields $W$, and the $\int d^4θ$-integrand is restricted only by gauge in

D. E. Jaramillo, J. H. Munoz, A. Zepeda

Some textbooks and reports claim that the Jacobian which arises in the discussion of the Faddeev-Popov method to quantize non-Abelian gauge theories and which is given by the derivative of the gauge fixing conditions over the gauge group parameters, is gauge invariant. Other references however prove the opposite. In this brief report we present a discussion

Avijit K. Ganguly, Palash B. Pal

Performing functional integration of the free Lagrangian, we find the vacuum energy of a field. The functional integration is performed in a way which easily generalizes to systems at non-zero temperature. We use this technique to obtain the Casimir energy density and pressure at arbitrary temperatures.

Karim Benakli, John Ellis, Dimitri V. Nanopoulos

We reconsider superheavy dark matter candidates in string and M theory, in view of the possibility that inflation might generate superheavy particles with an abundance close to that required for a near-critical Universe. We argue that cryptons - stable or metastable bound states of matter in the hidden sector - are favoured over other possible candidates in

B. Krippa

The processes involving $K^{-}p, KN, Σπ, Λπ,Ση, Λη$ coupled channels are studied in the nonperturbative chiral approach. An effective potential is constructed using a chiral meson-baryon Lagrangian at lowest order. This potential is iterated to all orders with the Lippmann-Schwinger equation. A reasonable fit of the experimental data is obtained. It is point

J. -M. Gerard, J. Pestieau, J. Weyers

Hadronic phase in $ππ$ and $K \bar K$ channels are calculated a la Regge. At the D mass one finds $δ_{ππ} \approx π/3$ and $δ_{K \bar K} \approx -π/6$ in good agreement with the CLEO data while at the B mass these angles are predicted to be, respectively, $11^\circ$ and $-7^\circ$. With the hadronic phase $e^{i δ_{K \bar K}}$ taken into account, a quark diag

K. Kolodziej, R. Rückl

An estimate is presented of the production cross section of $B_c$ mesons between threshold and LHC energies using lowest-order perturbation theory and non-relativistic bound state approximation. It is shown that the ratio of the production cross sections for $B_c$ mesons and for $b$ quarks varies strongly with energy.

Chris Quigg

The eventual prospect of muon colliders reaching several TeV encourages us to consider the experimental opportunities presented by very copious stores of muons, approaching $10^{21}$ per year. I summarize and comment upon some highlights of the Fermilab Workshop on Physics at the First Muon Collider and at the Front End of a Muon Collider. Topics include var

F. O. Durães, F. S. Navarra, G. Wilk

Recent DESY-HERA data on $J/Ψ$ elasticity distribution show that it emerges mostly as a fast particle. Interpreting photoproduction as a collision between a pre-formed charmed hadron and the proton, the outcoming $J/Ψ$ is a leading particle of the collision. We analyse these data using a model formulated to describe energy flow in hadron-hadron reactions. Th

A. G. Akeroyd

The phenomenology of neutral Higgs bosons from non--SUSY, extended Higgs sectors is studied in the context of the LHC, with particular attention given to the case of a fermiophobic Higgs. It is found that enhanced branching ratios to $γγ$ and $τ^+τ^-$ are possible and can provide clear signatures, while detection of a fermiophobic Higgs will be problematic b

W. Krolikowski

A unified form of mass matrix proposed previously for all fundamental fermions is extended to include the sterile neutrino $ν_s$, presumed to mix mainly with $ν_e$, while $ν_τ$ mixes strongly with $ν_μ$ (and both $ν_μ$ and $ν_τ$ weakly with $ν_e$ and $ν_s$). It turns out that the former mixing can be responsible for oscillations of solar neutrinos, while the

G. K. Leontaris, N. D. Tracas

Lepton flavour non-conserving processes are examined in the context of unified models with U(1)-family symmetries which reproduce successfully the low-energy hierarchy of the fermion mass spectrum and the Kobayashi - Maskawa mixing. These models usually imply mixing effects in the supersymmetric scalar sector. We construct the fermion and scalar mass matrice

Jonathan L. Feng

Advantages of the e-e- option at linear colliders for the study of supersymmetry are highlighted. The fermion number violating process $e^- e^- \to \selectron^- \selectron^-$ provides unique opportunities for studies of slepton masses and flavor mixings. In particular, slepton mass measurements at the 100 MeV level through threshold scans of scalar pair prod

Yasuhiro Okada

Theoretical aspects of kaon and muon decays are reviewed. In particular, three topics on kaon and muon decays, namely $K \to πν\barν$ processes, T violation in $K^+ \to π^0μ^+ ν$ decay and lepton flavor violation in muon decay are considered. Theoretical backgrounds and possible significance on new physics searches by these processes are discussed.

V. Gupta, R. Huerta, G. Sanchez-Colon

Spin-1/2 baryons are considered as a composite system made out of a &#34;core&#34; of three quarks surrounded by a &#34;sea&#34; (of gluons and $q\bar{q}$-pairs) which is specified by its total quantum numbers. Specifically, we assume this sea to be a flavor octet with spin-0 or 1 but no color. We show our model can provide very goods fits to magnetic moment

Penelope A. Kasper

BTeV is a proposed forward collider program at the Fermilab Tevatron dedicated to precision studies of CP violation, mixing and rare decays of beauty and charm hadrons. A description of the proposed detector and results of simulations of several physics channels are presented.

E. A. Hawker, T. C. Awes, M. E. Beddo, C. N. Brown

A precise measurement of the ratio of Drell-Yan yields from an 800 GeV/c proton beam incident on hydrogen and deuterium targets is reported. Over 140,000 Drell-Yan muon pairs with dimuon mass M_{mu+ mu-} >= 4.5 GeV/c^2 were recorded. From these data, the ratio of anti-down (dbar) to anti-up (ubar) quark distributions in the proton sea is determined over a wi

K. Edwards

We present new measurements of photon energies and branching fractions for the radiative transitions: Upsilon(2S)->gamma+chi_b(J=0,1,2). The masses of the chi_b states are determined from the measured radiative photon energies. The ratio of mass splittings between the chi_b substates, r==(M[J=2]-M[J=1])/(M[J=1]-M[J=0]) with M the chi_b mass, provides informa

G. A. Monerat, H. P. de Oliveira, Ivano D. Soares

The dynamics of a preinflacionary phase of the universe, and its exit to inflation, is discussed. This phase is modeled by a closed Friedmann-Robertson-Walker geometry, the matter content of which is radiation plus a scalar field minimally coupled to the gravitational field. The simple configuration, with two effective degres of freedom only, presents a very

R. Parentani

We analyze the Hamilton-Jacobi action of gravity and matter in the limit where gravity is treated at the background field approximation. The motivation is to clarify when and how the solutions of the Wheeler-DeWitt equation lead to the Schrödinger equation in a given background. To this end, we determine when and how the total action, solution of the constra

A. N. Aliev, M. Hortacsu, N. Ozdemir

We study the interaction of a massless quantized spinor field with the gravitational filed of N parallel static cosmic strings by using a perturbative approach. We show that the presence of more than one cosmic string gives rise to an additional contribution to the energy density of vacuum fluctuations, thereby leading to a vacuum force attraction between tw

J. Fernando Barbero G., Alfredo Tiemblo, Romualdo Treseguerres

We study the Husain-Kuchar model by introducing a new action principle similar to the self-dual action used in the Ashtekar variables approach to Quantum Gravity. This new action has several interesting features; among them, the presence of a scalar time variable that allows the definition of geometric observables without adding new degrees of freedom, the a

Ion I. Cotăescu

It is shown that, for spherically symmetric static backgrounds, a simple reduced Dirac equation can be obtained by using the Cartesian tetrad gauge in Cartesian holonomic coordinates. This equation is manifestly covariant under rotations so that the spherical coordinates can be separated in terms of angular spinors like in special relativity, obtaining a pai

Vladimir S. Mashkevich

This paper is a sequel to the series of papers [gr-qc/9409010, gr-qc/9505034, gr-qc/9603022, gr-qc/9609035, gr-qc/9609046, gr-qc/9704033, gr-qc/9704038, gr-qc/9708014, gr-qc/9802016, gr-qc/9802022]. We define a quantum measurement as a sequence of binary quantum jumps caused by a macroscopic apparatus. A dynamical theory of measurement is developed, the role

Shanhui Xiong

The duality in the Chalker-Coddington network model is examined. We are able to write down a duality relation for the edge state transmission coefficient, but only for a specific symmetric Hall geometry. Looking for broader implication of the duality, we calculate the transmission coefficient $T$ in terms of the conductivity $σ_{xx}$ and $σ_{xy}$ in the diff

Jordan Kyriakidis, Daniel Loss

We study the quantum dynamics of soliton-like domain walls in anisotropic spin-1/2 chains in the presence of magnetic fields. In the absence of fields, domain walls form a Bloch band of delocalized quantum states while a static field applied along the easy axis localizes them into Wannier wave packets and causes them to execute Bloch oscillations, i.e. the d

Nikolai Brilliantov

We develop further the approach of Hubbard and Schofield (Phys.Lett., A40 (1972) 245), which maps the fluid Hamiltonian onto a magnetic one. We show that all coefficients of the resulting effective Landau-Ginzburg-Wilson (LGW) Hamiltonian may be expressed in terms of the compressibility of a reference fluid containing only repulsive interactions, and its den

D. D. Sarma, A. Chainani, S. R. Krishnakumar, E. Vescovo

Investigating LaNi(1-x)M(x)O3 (M = Mn and Fe), we identify a characteristic evolution of the spectral function with increasing disorder in presence of strong interaction effects across the metal-insulator transition. We discuss these results vis-a-vis existing theories of electronic structure in simultaneous presence of disorder and interaction.

S. A. Vitkalov

A new model of momentum and electric field transfer between two adjacent 2D electron systems in the Quantum Hall Effect is proposed. The drag effect is due to momentum transfer from the vortex system of one layer to the vortex system of another layer. The remarkable result of this approach is periodical change of $sign$ of the dragged electric field with dif

H. -J. Schmidt, J. Schnack

Recursion formulae of the N-particle partition function, the occupation numbers and its fluctuations are given using the single-particle partition function. Exact results are presented for fermions and bosons in a common one-dimensional harmonic oscillator potential, for the three-dimensional harmonic oscillator approximations are tested. Applications to exc

N. B. Ivanov, J. Richter, U. Schollwoeck

We study the ground-state properties of weakly frustrated Heisenberg ferrimagnetic chains with nearest and next-nearest neighbor antiferromagnetic exchange interactions and two types of alternating sublattice spins S_1 > S_2, using 1/S spin-wave expansions, density-matrix renormalization group, and exact- diagonalization techniques. It is argued that the zer

Mario Nicodemi, Antonio Coniglio

In the framework of recently introduced frustrated lattice gas models, we study the out of equilibrium dynamical processes during the compaction process in granular media. We find irreversible-reversible cycles in agreement with recent experimental observations. Moreover in analogy with the phenomenology of the glass transition we find aging effects during t

K-H Muetter, A Schmitt, M Karbach, Y. Yu

The excitation spectra of the T=0 dynamic structure factors for the spin, dimer, and trimer fluctuation operators as well as for the newly defined center fluctuation operator in the one-dimensional S=1 Heisenberg model wi th isotropic bilinear $(J\cosθ)$ and biquadratic $(J\sinθ)$ exchange are investigated via the recursion method for systems with up to N=18

E. Milshtein, O. Biham, S. Solomon

Universality in isotropic, abelian and non-abelian, sandpile models is examined using extensive numerical simulations. To characterize the critical behavior we employ an extended set of critical exponents, geometric features of the avalanches, as well as scaling functions describing the time evolution of average quantities such as the area and size during th

R. Schumann

Based on the special properties of Liouville eigenoperators a perturbation theory for the partition sum is given. It is applicable for any temperature and includes the case of degenerate Hamiltonians. To demonstrate the reliability of the method, the second order correction to the atomic limit grand canonical potential of the Hubbard model is calculated and

Govindan Rangarajan, Salman Habib, Robert D. Ryne

We present a new method for the computation of Lyapunov exponents utilizing representations of orthogonal matrices applied to decompositions of M or MM_trans where M is the tangent map. This method uses a minimal set of variables, does not require renormalization or reorthogonalization, can be used to efficiently compute partial Lyapunov spectra, and does no

A. Kudrolli, B. Pier, J. P. Gollub

We report novel superlattice wave patterns at the interface of a fluid layer driven vertically. These patterns are described most naturally in terms of two interacting hexagonal sublattices. Two frequency forcing at very large aspect ratio is utilized in this work. A superlattice pattern (&#34;superlattice-I&#34;) consisting of two hexagonal lattices oriente

D. K. Duncan, L. M. Rebull, F. Primas, A. M. Boesgaard

The Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) has been used to observe the boron 2500 A region of BD-13 3442. At a metallicity of [Fe/H]=-3.00, this is the most metal-poor star ever observed for B. Nearly 26 hours of exposure time resulted in a detection. Spectrum synthesis using the latest Kurucz model atmospheres yield

D. T. Frayer, E. R. Seaquist, T. X. Thuan, A. Sievers

We report on observations of CO(1-0) emission from the chemically young starburst galaxy Mrk 109. These observations were part of a study to constrain the O2/CO ratio in metal-deficient galaxies, which were motivated by theoretical work that suggests the possible enhancement of the O2/CO ratio in chemically young systems. Five low metallicity (Z < 0.5 Z(sola

Stephen Levine, Linda Sparke

Many disk galaxies are lopsided: their brightest inner parts are displaced from the center of the outer isophotes, or the outer contours of the HI disk. This asymmetry is particularly common in small, low-luminosity galaxies. We argue here that long-lived lopsidedness is a consequence of the disk lying off-center in the potential of the galaxy&#39;s extended

R. I. Hynes, C. A. Haswell, C. R. Shrader, W. Chen

We report on the results of a campaign to observe the SXT GRO J1655-40 in outburst using HST, XTE and GRO and AAT. This outburst was qualitatively quite different to other SXT outbursts and to previous outbursts of this source. The onset of hard X-ray activity occurred very slowly, over several months and was delayed relative to the soft X-ray rise. During t

Rien van de Weygaert, Francis Bernardeau

We describe two new -- stochastic-geometrical -- methods to obtain reliable velocity field statistics from N-body simulations and from any general density and velocity fluctuation field sampled at a discrete set of locations. These methods, the Voronoi tessellation method and Delaunay tessellation method, are based on the use of the Voronoi and Delaunay tess

Yurij V. Baryshev, Francesco Sylos Labini, Marco Montuori, Luciano Pietronero

Two fundamental empirical laws have been established in the analysis of galaxy space distribution. First, recent analyses have revealed that the three dimensional distribution of galaxies and clusters is characterized by large scale structures and huge voids: such a distribution shows fractal correlations up to the limits of the available samples. This has c

Ramesh Narayan, Rohan Mahadevan, Eliot Quataert

This article reviews the physics of advection-dominated accretion flows (ADAFs) and describes applications to several black hole X-ray binaries and galactic nuclei. The possibility of using ADAFs to explore the event horizons of black holes is highlighted.

I. A. G. Snellen, R. T. Schilizzi, A. G. de Bruyn, G. K. Miley

The Westerbork Northern Sky Survey (WENSS) has been used to select a sample of Gigahertz Peaked Spectrum (GPS) radio sources at flux densities one to two orders of magnitude lower than bright GPS sources investigated in earlier studies. Sources with inverted spectra at frequencies above 325 MHz have been observed with the WSRT at 1.4 and 5 GHz and with the V

Uta Fritze-v. Alvensleben

We analyse the population of bright star clusters in the interacting galaxy pair NGC 4038/39 detected with HST WFPC1 by Whitmore & Schweizer (1995) using our spectrophotometric evolutionary synthesis models for various initial metallicities. We derive individual ages for all clusters with V-I colour and follow the time evolution of their luminosity function

Creidhe O&#39;Sullivan, A. Shearer, M. Colhoun, A. Golden

Using time-resolved two-dimensional aperture photometry we have put upper limits on the pulsed emission from two proposed optical counterparts for PSR B1951+32. Our pulsed upper limits of m_{vpulsed}>23.3, m_{bpulsed}>24.4$, for the first candidate and m_{vpulsed}>23.6$, m_{bpulsed}>24.3 for the second, make it unlikely that either of these is, in fact, the

Wolfgang Ebeling, Sabir M. Gusein-Zade

We consider manifolds with isolated singularities, i.e., topological spaces which are manifolds (say, $C^\infty$--) outside discrete subsets (sets of singular points). For (germs of) manifolds with, so called, cone--like singularities, a notion of the index of an isolated singular point of a vector field is introduced. There is given a formula for the index

S. W. Sides, P. A. Rikvold, M. A. Novotny

We study hysteresis for a two-dimensional, spin-1/2, nearest-neighbor, kinetic Ising ferromagnet in an oscillating field, using Monte Carlo simulations. The period-averaged magnetization is the order parameter for a proposed dynamic phase transition (DPT). To quantify the nature of this transition, we present the first finite-size scaling study of the DPT fo

M. Asaeda, U. Haagerup

We prove existence of subfactors of finite depth of the hyperfinite II_1 factor with indices (5+sqrt{13})/2= 4.302... and (5+sqrt{17})/2=4.561.... The existence of the former was announced by the second named author in 1993 and that of the latter has been conjectured since then. These are the only known subfactors with finite depth which do not arise from cl

A. Ali, H. Asatrian, C. Greub

We compute the decay rate for the CKM-suppressed electromagnetic penguin decay $B \to X_d + γ$ (and its charge conjugate) in NLO QCD, including leading power corrections in $1/m_b^2$ and $1/m_c^2$ in the standard model. The average branching ratio of the decay $B \to X_dγ$ and its charge conjugate is estimated to be in the range $6.0 \times 10^{-6} \leq <BR(

Matteo Bertolini, Pietro Fre`, Roberto Iengo, Claudio A. Scrucca

We show how an extremal Reissner-Nordstrom black hole can be obtained by wrapping a dyonic D3-brane on a Calabi-Yau manifold. In the orbifold limit T^6/Z_3, we explicitly show the correspondence between the solution of the supergravity equations of motion and the D-brane boundary state description of such a black hole.

Robert Baur, Joachim Kambor

Standard SU(2) Heavy Baryon Chiral Perturbation Theory is extended in order to include the case of small or even vanishing quark condensate. The effective lagrangian is given to ${\cal O}(p^2)$ in its most general form and to ${\cal O}(p^3)$ in the scalar sector. A method is developed to efficiently construct the relativistic baryonic effective lagrangian fo

Sven Bergmann, Alex Kagan

Adding singlet neutrinos to the standard model spectrum in general gives rise to Z-induced flavor-changing neutral currents. We study the impact of these currents on matter-induced neutrino oscillations in the sun and in supernovae. While the effects for solar neutrinos are negligible, dramatic effects are possible for supernova neutrinos.

Rajib Ganguly, Christopher W. Churchill, Jane C. Charlton

In the z=1.94 CIV absorption line system in the spectrum of quasar Q1222+228 (z_em=2.04), we find two clouds which have contrasting physical conditions, although they are only at a 17 km/s velocity separation. In the first cloud SiII, SiIV, and CII are detected, and AlII and AlIII column density limits in conjunction with photoionization models allow us to i

Fyodor Malikov, Vadim Schechtman, Arkady Vaintrob

The aim of this note is to define certain sheaves of vertex algebras on smooth manifolds. For each smooth complex algebraic (or analytic) manifold $X$, we construct a sheaf $Ω^{ch}_X$, called the {\bf chiral de Rham complex} of $X$. It is a sheaf of vertex algebras in the Zarisky (or classical) topology, It comes equipped with a $\BZ$-grading by {\it fermion

Z. K. Silagadze

A general pedagogical survey of the basics of the Bethe-Salpeter equation and in particular Wick-Cutkosky model is given in great technical details.