March 1999 arXiv papers — page 4

Lajos Diosi

In the Copenhagen viewpoint, part of the world is quantized and the complementary part remains classical. From a formal dynamic aspect, standard theory is incomplete since it does never account for the so-called 'back-reaction' of quantized systems on classical systems except for the highly idealized system-detector interaction. To resolve this forma

A. J. Bracken, G. F. Melloy

A causally well-behaved solution of the localization problem for the free electron is given, with natural space-time transformation properties, in terms of Dirac's position operator. It is shown that, although this operator does not represent an observable in the usual sense, and has no positive-energy (generalized) eigenstates, the associated 4-vector d

Siva Athreya, Roger Tribe

For independent nearest-neighbour bond percolation on Z^d with d >> 6, we prove that the incipient infinite cluster's two-point function and three-point function converge to those of integrated super-Brownian excursion (ISE) in the scaling limit. The proof is based on an extension of the new expansion for percolation derived in a previous paper, and invo

Siddhartha Bhattacharya

In this paper we study topological rigidity of affine actions on compact connected metrizable abelian groups. We also classify one-parameter flows of translations upto orbit equivalence and discrete group actions by translations upto topological conjugacy.

L. Katzarkov, T. Pantev

In this paper we generalize to the non-abelian context a classical theorem of Griffiths which studies the behavior of the $(p,q)$-components of a horizontal section in a variation of Hodge structures over a smooth projective variety.

Tahl Nowik

Given a surface F, we are interested in Z/2 valued invariants of immersions of F into R^3, which are constant on each connected component of the complement of the quadruple point discriminant in Imm(F,R^3). Such invariants will be called ``q-invariants.'' Given a regular homotopy class A in Imm(F,R^3), we denote by V_n(A) the space of all q-invariant

Michael Polyak, Oleg Viro

We study the Vassiliev knot invariant v_2 of degree 2. We present it via the degrees of maps of various configuration spaces related to a knot to products of spheres. This gives rise to numerous geometrical and combinatorial formulas for this invariant.

Dmitriy S. Kalyuzhniy

In the present paper we introduce the notion of dilation of a multiparametric linear stationary dynamical system (systems of this type, in particular passive, and conservative scattering ones were first introduced in func-an/9804130). We establish the criterion for existence of a conservative dilation of a multiparametric passive scattering system. This allo

Eduardo I. Guendelman, Emil Nissimov, Svetlana Pacheva

We describe new theories of composite vector and tensor (p-form) gauge fields made out of zero-dimensional constituent scalar fields (``primitives''). The local gauge symmetry is replaced by an infinite-dimensional global Noether symmetry -- the group of volume-preserving (symplectic) diffeomorphisms of the target space of the scalar primitives. We f

Maximo Banados

These notes are the written version of two lectures delivered at the VIII Mexican School on Particles and Fields on November 1998. The level of the notes is basic assuming only some knowledge on Statistical Mechanics, General Relativity and Yang-Mills theory. After a brief introduction to the classical and semiclassical aspects of black holes, we review some

Michael Melles, W. James Stirling

The experimental determination of the partial width $Γ(H \longrightarrow γγ)$ of an intermediate mass Higgs is among the most important measurements at a future photon photon collider. Recently it was shown that large non-Sudakov as well as Sudakov double logarithmic (DL) corrections can be summed to all orders in the background process $γγ(J_z=0) \longright

D. P. Roy

After a brief introduction to neutrino mass via the see-saw model I discuss neutrino mixing and oscillation, first in vacuum and then its matter enhancement. Then the solar and atmospheric neutrino oscillation data are briefly reviewed. Finally I discuss the problem of reconciling hierarchical neutrino masses with at least one large mixing, as implied by the

A. Gonzalez-Arroyo

We derive a series of results on random walks on a d-dimensional hypercubic lattice (lattice paths). We introduce the notions of terse and simple paths corresponding to the path having no backtracking parts (spikes). These paths label equivalence classes which allow a rearrangement of the sum over paths. The basic combinatorial quantities of this constructio

Andrzej Krolak

The main problem that we will face in the data analysis for continuous gravitational-wave sources is processing of a very long time series and a very large parameter space. We present a number of analytic and numerical tools that can be useful in such a data analysis. These consist of methods to calculate false alarm probabilities, use of probabilistic algor

Robert J. Budzynski, Witold Kondracki, Andrzej Krolak

Chrusciel and Galloway constructed a Cauchy horizon that is nondifferentiable on a dense set. We prove that in a certain class of Cauchy horizons densely nondifferentiable Cauchy horizons are generic. We show that our class of densely nondifferentiable Cauchy horizons implies the existence of densely nondifferentiable Cauchy horizons arising from partial Cau

M. Meier-Schellersheim, G. Mack

We present a new approach to the simulation and analysis of immune system behavior. The simulations that can be done with our software package called SIMMUNE are based on immunological data that describe the behavior of immune system agents (cells, molecules) on a microscopial (i.e. agent-agent interaction) scale by defining cellular stimulus-response mechan

Karl Forster, Karen M. Leighly, Laura E. Kay

The X-ray spectra of two intermediate type Seyfert galaxies are investigated using ASCA observations separated by more than a year. Both NGC 4388 and ESO 103-G35 exhibit strong, narrow Fe K alpha line emission and absorption by cold neutral gas with a column density ~ 10^23 cm^-2, characteristic of the X-ray spectra of type 2 Seyfert galaxies. The power law

S. K. Leggett, D. W. Toomey, T. R. Geballe, R. H. Brown

We have used the coronographic instrument CoCo with the IRTF's facility camera NSFCAM to obtain improved photometry at JHKL' of the giant planet/brown dwarf Gliese 229B. We have recalibrated the published spectra for this object, and re-calculated its luminosity. Our L' value, and our flux calibration of the spectra at JHK, are significantly diff

Paul R. Shapiro, Ilian T. Iliev, Alejandro C. Raga

The postcollapse structure of objects which form by gravitational condensation out of the expanding cosmological background universe is a key element in the theory of galaxy formation. Towards this end, we have reconsidered the outcome of the nonlinear growth of a uniform, spherical density perturbation in an unperturbed background universe - the cosmologica

Yuhsuke Yoshida, Takahiro Kubota

We describe the Brown-Henneaux asymptotic symmetry of the general black holes in the Chern-Simons gauge theory of the gauge group $SL(2;{\bf R})_L\times SL(2;{\bf R})_R$. We make it clear that the vector-like subgroup $SL(2; {\bf R})_{L+R}$ plays an essential role in describing the asymptotic symmetry consistently. We find a quite general black hole solution

J. S. Høye, I. Brevik

The Casimir energy for a compact dielectric sphere is considered in a novel way, using the quantum statistical method introduced by H\oye - Stell and others. Dilute media are assumed. It turns out that this method is a very powerful one: we are actually able to derive an expression for the Casimir energy that contains also the negative part resulting from th

Dima Mozyrsky, Vladimir Privman

We present an exact derivation of a process in which a microscopic measured system interacts with "heat bath" and pointer modes of a measuring device, via a linear coupling involving Hermitian operator $Λ$ of the system. In the limit of strong interaction with these modes, over a small time interval, we show that the measured system and the "poin

D. Kaledin

Let $V$ be a complex vector space on which a finite group $G$ acts by linear transformations. Let $W = V \oplus V^*$ be the sum of $V$ with its dual $V^*$. We prove that if the quotient $W/G$ admits a smooth crepant resolution, then the subgroup $G \subset Aut V$ is generated by complex reflections. We also obtain some results on the structure of smooth crep

Yang-Hui He, Jun S. Song

The ubiquitous ADE classification has induced many proposals of often mysterious correspondences both in mathematics and physics. The mathematics side includes quiver theory and the McKay Correspondence which relates finite group representation theory to Lie algebras as well as crepant resolutions of Gorenstein singularities. On the physics side, we have the

M. Tanimoto

I review models which present large flavor mixings of the lepton sector based on the gauge theory.

S. Heinemeyer, W. Hollik, G. Weiglein

The masses of the neutral CP-even Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM) are predicted on the basis of explicit Feynman-diagrammatic calculations. The results, containing the complete diagrammatic one-loop corrections, the leading two-loop corrections of O(alpha alpha_s) and further improvements taking into account leading electrowe

Mark D. Roberts

There exists a two parameter action, the variation of which produces both the geodesic equation and the geodesic deviation equation. In this paper it is shown that this action can be quantized by the canonical method, resulting in equations which generalize the Klein-Gordon equation. The resulting equations might have applications, and also show that entirel

U. S. Schwarz, G. Gompper

The Fourier approach and theories of space groups and color symmetries are used to systematically generate and compare bicontinuous cubic structures in the framework of a Ginzburg-Landau model for ternary amphiphilic systems. Both single and double structures are investigated; they correspond to systems with one or two monolayers in a unit cell, respectively

Toru Sakai, Minoru Takahashi

The magnetization process of the one-dimensional antiferromagnetic Heisenberg model with the Ising-like anisotropic exchange interaction is studied by the exact diagonalization technique. It results in the evidence of the first-order spin flop transition with a finite magnetization jump in the Néel ordered phase for $S\geq 1$. It implies that the S=1/2 chain

M. W. Lee, D. Sornette

Numerical simulations and a mean-field analysis of a sandpile model of earthquake aftershocks in 1d, 2d and 3d euclidean lattices determine that the average stress decays in a punctuated fashion after a main shock, with events occurring at characteristic times increasing as a geometrical series with a well-defined multiplicative factor which is a function of

Robert W. O'Connell

Rapid progress is now being made in the study of stellar populations of galaxies at large lookback times, both in dense clusters and the field. Dramatic transformations in star formation histories (even morphologies) appear to prevail among all types of galaxies and in all environments, and these can be traced to relatively recent times (z ~ 0.2). This artic

Penny D. Sackett

Techniques for inferring the radial and geometric form of dark matter halos and the results they have produced to date are reviewed. Dark halos appear to extend to at least ~50 kpc with total enclosed masses that rise linearly with radius R. Whether this behavior can be extrapolated to distances as large as 200 kpc and beyond is controversial; results at thi

Geoffrey C. Clayton, F. Kerber, Karl D. Gordon, Warrick A. Lawson

We present new images of the reflection nebula surrounding the R Coronae Borealis Star, UW Cen. This nebula, first detected in 1990, has changed its appearance significantly. At the estimated distance of UW Cen, this nebula is approximately 0.6 ly in radius so the nebula cannot have physically altered in only 8 years. Instead, the morphology of the nebula ap

Roberto Emparan, Clifford V. Johnson, Robert C. Myers

We examine the recently proposed technique of adding boundary counterterms to the gravitational action for spacetimes which are locally asymptotic to anti-de Sitter. In particular, we explicitly identify higher order counterterms, which allow us to consider spacetimes of dimensions d<=7. As the counterterms eliminate the need of ``background subtraction&#39;

M. Alford, J. Berges, K. Rajagopal

We explore the phase diagram of strongly interacting matter with massless u and d quarks as a function of the strange quark mass m_s and the chemical potential mu for baryon number. Neglecting electromagnetism, we describe the different baryonic and quark matter phases at zero temperature. For quark matter, we support our model-independent arguments with a q

Vassiliki Kalogera, Dimitrios Psaltis

Recent X-ray variability observations of accreting neutron stars may provide the first evidence for frame dragging effects around spinning relativistic objects. Motivated by this possibility and its implications for neutron-star structural properties, we calculate new optimal bounds on the masses, radii, and moments of inertia of slowly rotating neutron star

D. A. Lowe, L. Thorlacius

The information paradox in the quantum evolution of black holes is studied within the framework of the AdS/CFT correspondence. The unitarity of the CFT strongly suggests that all information about an initial state that forms a black hole is returned in the Hawking radiation. The CFT dynamics implies an information retention time of order the black hole lifet

H. Kachkachi, A. Ezzir, M. Nogues, E. Tronc

We present a microscopic model for nanoparticles, of the maghemite ($γ$% -Fe$_{2}$O$_{3}$) type, and perform classical Monte Carlo simulations of their magnetic properties. On account of Mössbauer spectroscopy and high-field magnetisation results, we consider a particle as composed of a core and a surface shell of constant thickness. The magnetic state in th

N. Andrenacci, A. Perali, P. Pieri, G. C. Strinati

We investigate the zero-temperature BCS to Bose-Einstein crossover at the mean-field level, by driving it with the attractive potential and the particle density.We emphasize specifically the role played by the particle density in this crossover.Three different interparticle potentials are considered for the continuum model in three spatial dimensions, while

A. Mourachkine

We present electron-tunneling spectroscopy of slightly overdoped Bi2212 single crystals with Tc = 87 - 90 K in a temperature range between 14 K and 290 K using a break-junction technique. The pseudogap which has been detected above Tc appears at T* = 280 K. The analysis of the spectra shows that there is a contribution to the pseudogap above Tc, which disapp

H. J. de Vega, N. S&#39;anchez

We provide a complete picture of the self-gravitating non-relativistic gas at thermal equilibrium using Monte Carlo simulations (MC), analytic mean field methods (MF) and low density expansions. The system is shown to possess an infinite volume limit, both in the canonical (CE) and in the microcanonical ensemble (MCE) when N, V \to \infty, keeping N/ V^{1/3}

V. S. Khrapai, E. V. Deviatov, A. A. Shashkin, V. T. Dolgopolov

We investigate the double-layer electron system in a parabolic quantum well at filling factor $ν=2$ in a tilted magnetic field using capacitance spectroscopy. The competition between two ground states is found at the Zeeman splitting appreciably smaller than the symmetric-antisymmetric splitting. Although at the transition point the system breaks up into dom

Valentin Vankov Iliev

The aim of this paper is to present a generalization of Lunn-Senior&#39;s mathematical model of isomerism in organic chemistry. The main idea of Lunn and Senior is that if the type of isomerism is fixed, a molecule with a fixed skeleton and d univalent substituents has a symmetry group $W\leq S_d$ which is generally not the molecule&#39;s 3-dimensional symme

Akira Fujii, Ryuji Kemmoku

The Kaluza-Klein spectrum of D=5 simple supergravity compactified on S^3 is studied. A classical background solution which preserves maximal supersymmetry is fulfilled by the geometry of AdS_2\times S^3. The physical spectrum of the fluctuations is classified according to SU(1,1|2)\times SU(2) symmetry, which has a very similar structure to that in the case

Fumiko Takagi, Tsuyoshi Hondou

Molecular motors in biological systems are expected to use ambient fluctuation. In a recent Letter [Phys. Rev. Lett. {\bf 80}, 5251 (1998)], it was showed that the following question was unsolved, ``Can thermal noise facilitate energy conversion by ratchet system?&#39;&#39; We consider it using stochastic energetics, and show that there exist systems where t

T. Nagano, A. Ota, Y. Sumino

Recently full O(alpha_s^2, alpha_s*beta, beta^2) corrections to the threshold total cross section for e+e- to ttbar have been calculated, and the reported corrections turned out to be unexpectedly large. We study how to reduce theoretical uncertainties of the cross section. We adopt a new mass definition proposed by Beneke, which incorporates a renormalon-po

Jeong-Hyuck Park

Four-dimensional N-extended superconformal symmetry and correlation functions of quasi-primary superfields are studied within the superspace formalism. A superconformal Killing equation is derived and its solutions are classified in terms of supertranslations, dilations, Lorentz transformations, R-symmetry transformations and special superconformal transform

Ho-Meoyng Choi, Chueng-Ryong Ji

We present the analysis of exclusive $0^{-}$$\to$$0^{-}$ semileptonic heavy meson decays using the constituent quark model based on the light-front quantization. Our model is constrained by the variational principle for the well-known linear plus Coulomb interaction motivated by QCD. Our method of analytic continuation to obtain the weak form factors avoids

R. B. Mann

I show that gravitational entropy can be ascribed to spacetimes containing Misner strings (the gravitational analogues of Dirac strings), even in the absence of any other event horizon (or bolt) structures. This result follows from an extension of proposals for evaluating the stress-energy of a gravitational system which are motivated by the AdS/CFT correspo

M. Cvetic, M. J. Duff, P. Hoxha, James T. Liu

We construct the non-linear Kaluza-Klein ansätze describing the embeddings of the U(1)^3, U(1)^4 and U(1)^2 truncations of D=5, D=4 and D=7 gauged supergravities into the type IIB string and M-theory. These enable one to oxidise any associated lower dimensional solutions to D=10 or D=11. In particular, we use these general ansätze to embed the charged AdS_5,

Joseph Polchinski, Leonard Susskind, Nicolaos Toumbas

The holographic connection between large $N$ Super Yang Mills theory and gravity in anti deSitter space requires unfamiliar behavior of the SYM theory in the limit that the curvature of the AdS geometry becomes small. The paradoxical behavior includes superluminal oscillations and negative energy density. These effects typically occur in the SYM description

Bernard Deconinck, Harvey Segur

The real, nonsingular elliptic solutions of the Korteweg-deVries equation are studied through the time dynamics of their poles in the complex plane. The dynamics of these poles is governed by a dynamical system with a constraint. This constraint is shown to be solvable for any finite number of poles located in the fundamental domain of the elliptic function,

A. K. Rajagopal, K. L Jensen, F. W. Cummings

The regions of independent quantum states, maximally classically correlated states, and purely quantum entangled (supercorrelated) states described in a recent formulation of quantum information theory by Cerf and Adami are explored here numerically in the parameter space of the well-known exactly soluable Jaynes-Cummings model for equilibrium and nonequilib

A. K. Rajagopal

We show that the Jaynes principle is indeed a proper inference scheme when applied to compound systems and will correctly produce the entangled maximum entropy states compatible with appropriate data. This is accomplished by including the dispersion of the entanglement along with its mean value as constraints and an application of the uncertainty principle.

Luca Sorriso-Valvo, Vincenzo Carbone, Pierluigi Veltri, Giuseppe Consolini

Intermittency in fluid turbulence can be emphasized through the analysis of Probability Distribution Functions (PDF) for velocity fluctuations, which display a strong non-gaussian behavior at small scales. Castaing et al. (1990) have introduced the idea that this behavior can be represented, in the framework of a multiplicative cascade model, by a convolutio

Alexander Moroz, Adriaan Tip

For the case of a simple face-centered-cubic photonic crystal of homogeneous dielectric spheres, we examine to what extent single-sphere Mie resonance frequencies are related to band gaps and whether the width of a gap can be enlarged due to nearby resonances. Contrary to some suggestions, no spectacular effects may be expected. When the dielectric constant

F. Ciesielski, J. Carbonell, C. Gignoux

The Faddeev-Yakubovsky equations have been solved in configuration space for the four nucleon system. The n+t elastic cross section has been calculated using several realistic interactions and a phenomenological three-nucleon force. Special attention is devoted to the description of the observed resonant structure at $T_{lab}\approx 4$ MeV. In the present st

Y. A. Abramovich, A. K. Kitover

This article contains the results of two types. First we give a complete characterization of band preserving projection operators on Dedekind complete vector lattices. This is done in Theorem~3.4. Let us mention also Theorem~3.2 that contains a description of such operators on arbitrary laterally complete vector lattices. The central role in these descriptio

Jian Zhou

We use Hodge theory and a construction of Merkulov to construct $A_{\infty}$ structures on de Rham cohomology and Dolbeault cohomology.

Jinho Baik, Percy Deift, Kurt Johansson

The authors consider the length, $l_N$, of the length of the longest increasing subsequence of a random permutation of $N$ numbers. The main result in this paper is a proof that the distribution function for $l_N$, suitably centered and scaled, converges to the Tracy-Widom distribution [TW1] of the largest eigenvalue of a random GUE matrix. The authors also

B. Kleihaus, J. Kunz

We point out that the statements in [hep-th/9903063] concerning the regularity of static axially symmetric solutions in Yang-Mills-dilaton (YMD) [1] and Einstein-Yang-Mills(-dilaton) (EYMD) theory [2,3] are incorrect, and that the non-singular local gauge potential of the YMD solutions [4] is twice differentiable.

Mitsuko Abe, Machiko Hatsuda, Kiyoshi Kamimura, Takashi Tokunaga

We propose a type IIB super-Poincare algebra with SO(2,1) covariant central extension. Together with SO(2,1) and SO(9,1) generators, a SO(2,1) triplet (momenta), a Majorana-spinor doublet (supercharges) and a Rarita-Schwinger central charge generate a group, G. We consider a coset G/H where H=(SO(2) x Lorentz), and the SL(2,R) 2-form doublet is obtained by t

Hiroshige Kajiura, Akishi Kato, Sachiko Ogushi

The large N Matrix model is studied with attention to the quantum fluctuations around a given diagonal background. Feynman rules are explicitly derived and their relation to those in usual Yang-Mills theory is discussed. Background D-instanton configuration is naturally identified as a discretization of momentum space of a corresponding QFT. The structure of

W. Lerche, S. Stieberger

We review interactions between certain 7-planes which are composed out of mutually non-local (p,q) 7-branes and which correspond to specific Kodaira singularities. We discuss in particular how to compute certain moduli-dependent terms in the effective action. These do not only probe the local Chern-Simons terms on the world-volumina, but also certain global

Akikazu Hashimoto

We describe a scheme for constructing the holographic dual of the full D3-brane geometry with charge $K$ by embedding it into a large anti-de Sitter space of size $N$. Such a geometry is realized in a multi-center anti-de Sitter geometry which admits a simple field theory interpretation as $SU(N+K)$ gauge theory broken to $SU(N) \times SU(K)$. We find that t

Thomas Schaefer, Frank Wilczek

We extend our proposal that major universality classes of hadronic matter can be understood, and in favorable cases calculated, directly in the microscopic quark variables, to allow for splitting between strange and light quark masses. A surprisingly simple but apparently viable picture emerges, featuring essentially three phases, distinguished by whether st

P. Belli, R. Bernabei, A. Bottino, F. Donato

The original annual-modulation region, singled out by the DAMA/NaI experiment for direct detection of WIMPs, is extended by taking into account the uncertainties in the galactic astrophysical velocities. Also the effect due to a possible bulk rotation for the dark matter halo is considered. We find that the range for the WIMP mass becomes 30 GeV < m_chi < 13

R. Sekhar Chivukula

In this talk I review modern theories of dynamical electroweak symmetry breaking and some of their signatures at Run II of the Tevatron collider.

Harald Fritzsch, Zhi-zhong Xing

We introduce a simple flavor symmetry breaking scheme, in which charged lepton masses have a strong hierarchy and neutrino masses are almost degenerate. It is possible to obtain a natural suppression of lepton flavor mixing between the 1st and 3rd families as well as the approximate decoupling of atmospheric and solar neutrino oscillations with nearly bi-max

Ambar Ghosal

Light Dirac neutrino of mass of mass of the order of few eV is obtained in an $SU(2)_L\times U(1)_Y$ model with an extended Higgs sector and right-handed neutrinos. Small neutrino mass is generated at the tree level through small effective coupling of the Dirac neutrino mass term due to soft discrete symmetry breaking. In order to remove the exact degeneracy

S. Mrenna

The connection between analytic and Monte Carlo calculations of soft gluon emission is reanalyzed in light of recent, theoretical developments in resummation. An alternative Monte Carlo algorithm is suggested which incorporates (1) corrections beyond leading order to the showering and (2) smoothly merges with the higher order calculation of single, hard part

K. Kinoshita

Semileptonic decays of B mesons may be used in many different ways to probe the CKM matrix. Presented here are several recent results from the CLEO II experiment, all involving the analysis or utilization of semileptonic B decays.

Vuko Brigljevic

We measure the mass, decay width and production rate of orbitally excited B mesons in 1.25 million hadronic Z decays registered by the L3 detector in 1994 and 1995. B meson candidates are inclusively reconstructed and combined with charged pions produced at the event primary vertex. An excess of events above the expected background is observed in the Bπmass

F. Parodi, P. Roudeau, A. Stocchi

A review of the current status of the Cabibbo-Kobayashi-Maskawa matrix (CKM) is presented. This paper is an update of the results published in [1]. The experimental constraints imposed by the measurements of ε_K, V_{ub}/V_{cb}, Δm_d and from the limit on Δm_d are used. Values of the constraints and of the parameters entering into the constraints, which restr

Volodymyr Pelykh

The generalization of Sommers--Sen spinor connection for spinor fields, associated with a distribution $V_4^3$ and on this basis the equations for Weyl and Dirac null vector fields on complexificated $V_4^3$ are obtained. We interpret the obtained results by examining the interaction of spinor fields with the inertial forces.

Andrew P. Billyard, Alan A. Coley, James E. Lidsey

A qualitative analysis is presented for spatially flat, isotropic and homogeneous cosmologies derived from the string effective action when the combined effects of a dilaton, modulus, two-form potential and central charge deficit are included. The latter has significant effects on the qualitative dynamics. The analysis is also directly applicable to the anis

Luis Craco

A spinless two-band model is studied in infinite dimension limit. Starting from the atomic limit, the formal exact solution of the model is obtained by means a perturbative treatment of the hopping and hybridisation terms. The model is solved in closed form in high dimensions assuming no local spin fluctuations. The non-Fermi liquid properties appearing in t

A. V. Chechkin, V. Yu. Gonchar

We propose the model, which allows us to approximate fractional Levy noise and fractional Levy motion. Our model is based (i) on the Gnedenko limit theorem for an attraction basin of stable probability law, and (ii) on regarding fractional noise as the result of fractional integration/differentiation of a white Levy noise. We investigate self - affine proper

V. F. Gantmakher, G. E. Tsydynzhapov, L. P. Kozeeva, A. N. Lavrov

A superconducting transition in the temperature dependence of the ab-plane resistivity of underdoped YBa_2Cu_3O_{6+x} crystals in the range T_c<30 K has been investigated. Unlike the case of samples with the optimal level of doping, the transition width increased insignificantly with magnetic field, and in the range T_c<13 K it decreased with increasing magn

Sergei A. Sergeenkov

Two novel phenomena in a weakly coupled granular superconductor under an applied stress are predicted which are based on recently suggested piezophase effect (a macroscopic quantum analog of the piezoelectric effect) in mechanically loaded grain boundary Josephson junctions. Namely, we consider the existence of stress induced paramagnetic moment in zero appl

Koji Hukushima

An efficient Monte Carlo method is extended to evaluate directly domain-wall free-energy for randomly frustrated spin systems. Using the method, critical phenomena of spin-glass phase transition is investigated in 4d +/-J Ising model under the replica boundary condition. Our values of the critical temperature and exponent, obtained by finite-size scaling, ar

Koujin Takeda, Toyohiro Tsurumaru, Ikuo Ichinose, Masaomi Kimura

System of Dirac fermions with random-varying mass is studied in detail. We reformulate the system by transfer-matrix formalism. Eigenvalues and wave functions are obtained numerically for various configurations of random telegraphic mass m(x). Localized and extended states are identified. For quasi-periodic m(x), low-energy wave functions are also quasi-peri

Dragi Karevski, Róbert Juhász, Loïc Turban, Ferenc Iglói

We consider the critical and off-critical properties at the boundary of the random transverse-field Ising spin chain when the distribution of the couplings and/or transverse fields, at a distance $l$ from the surface, deviates from its uniform bulk value by terms of order $l^{-κ}$ with an amplitude $A$. Exact results are obtained using a correspondence betwe

Atsushi Kaneko, Tomi Ohtsuki

Three-dimensional quantum percolation problems are studied by analyzing energy level statistics of electrons on maximally connected percolating clusters. The quantum percolation threshold $\pq$, which is larger than the classical percolation threshold $\pc$, becomes smaller when magnetic fields are applied, i.e., $\pq(B=0)>\pq(B\ne 0)>\pc$. The critical expo

B. Spivak, A. Zyuzin

We show that the sensitivity of wave speckle patterns in disordered nonlinear media to changes of scattering potential increases with sample size. For large enough sample size this quantity diverges, which implies that at given coherent wave incident on a sample there are multiple solutions for the spatial distribution of the wave&#39;s density. The number o

M. P. Sarachik, S. V. Kravchenko

We review recent experiments that provide evidence for a transition to a conducting phase in two dimensions at very low electron densities. The nature of this phase is not understood, and is currently the focus of intense theoretical and experimental attention.

G. Cicogna, M. Santoprete

Homoclinic chaos is usually examined with the hypothesis of hyperbolicity of the critical point. We consider here, following a (suitably adjusted) classical analytic method, the case of non-hyperbolic points and show that, under a Melnikov-type condition plus an additional assumption, the negatively and positively asymptotic sets persist under periodic pertu

J. P. Halpern, J. Kemp, T. Piran, M. A. Bershady

GRB 980519 had the most rapidly fading of the well-documented GRB afterglows, consistent with t^{-2.05 +/- 0.04} in BVRI as well as in X-rays during the two days in which observations were made. We report VRI observations from the MDM 1.3m and WIYN 3.5m telescopes, and we synthesize an optical spectrum from all of the available photometry. The optical spectr

Vassiliki Kalogera

We study theoretically the formation of black-hole (BH) X-ray binaries. Consistency of the models with the observed relative numbers of systems with low-mass (<2 M_sun) and intermediate-mass (~2 M_sun - M_{BH}) donors leads to severe constraints on the evolutionary parameters of the progenitors. In particular, we find that (i) BH progenitor masses cannot exc

B. J. Wallace, T. L. Landecker, P. M. W. Kalberla, A. R. Taylor

The HI environment of the Crab Nebula is investigated using 2.75&#39; and 9&#39; resolution data from (respectively) the DRAO Synthesis, and Effelsberg 100 m, radio telescopes. No clear evidence for an interaction between the Crab and the surrounding HI is found; the Crab probably lies within the boundaries of a large scale, low-density void in the HI distri

S. Aalto, S. Huettemeister, N. Z. Scoville, P. Thaddeus

[Abridged] The Owens Valley mm-Array has been used to map the CO 1--0 emission in the inner 2&#39;.5 of the grand design spiral galaxy M51 at 2&#39;&#39;-3&#39;&#39; resolution. The molecular spiral arms are revealed with unprecedented clarity: supermassive cloud complexes, Giant Molecular Associations, are for the first time resolved both along and perpendi

L. E. Montenegro, C. Yuan, B. G. Elmegreen

The stability of a rotating fluid disk to the formation of spiral arms is studied in the tightwinding approximation in the linear regime. The dispersion relation for spirals that was derived by Bertin et al. is shown to contain a new, acoustic instability beyond the Lindblad resonances that depends only on pressure and rotation. In this regime, pressure and

Eliot Quataert, Ramesh Narayan, Mark Reid

The radio source Sgr A* at the center of our Galaxy is believed to be a 2.6 x 10^6 solar mass black hole which accretes gas from the winds of nearby stars. We show that limits on the X-ray and infrared emission from the Galactic Center provide an upper limit of ~ 8 x 10^{-5} solar masses per year on the mass accretion rate in Sgr A*. The advection-dominated

P. Valageas, J. Silk

We incorporate quasars into an analytic model to describe the reheating and reionization of the universe. In combination with a previous study of galaxies and Lyman-$α$ clouds, we are able to provide a unified description of structure formation, verified against a large variety of observations. We also take into account the clumping of the baryonic gas in ad

Paul A. Crowther, Linda J. Smith

We present a study of the peculiar Galactic emission line object NaSt1 (WR122, IRAS 18497+0056) which has previously been classified as a Wolf-Rayet (WR) star. Our spectroscopic dataset comprises Keck I-HIRES, WHT-ISIS and UKIRT-CGS4 observations which show that NaSt1 has a highly reddened nebular spectrum with extremely strong permitted and forbidden lines

S. Huettemeister, S. Aalto, W. F. Wall

We present the first interferometric CO observations of the barred late-type galaxy UGC2855 and its companion UGC2866. UGC2855 is shown to belong to the rare class of galaxies with a long (~ 8kpc) continuous molecular bar. The velocity field along the bar is dominated by solid-body rotation and shows few perturbations. This, together with an almost constant

F. Mannucci, A. Ferrara

We report the discovery of a variable object in the Hubble Deep Field North (HDF-N) which has brightened, during the 8.5 days sampled by the data, by more than 0.9 mag in I and about 0.7 mag in V, remaining stable in B. Subsequent observations of the HDF-N show that two years later this object has dimmed back to about its original brightness in I. The colors

Tomasz Bulik, Krzysztof Belczynski, Wojciech Zbijewski

Compact object mergers are one of the currently favored models for the origin of GRBs. The discovery of optical afterglows and identification of the nearest, presumably host, galaxies allows the analysis of the distribution of burst sites with respect to these galaxies. Using a model of stellar binary evolution we synthesize a population of compact binary sy

Giovanni Vladilo

The main properties of Damped Lyman alpha (DLA) systems are briefly reviewed with the aim of studying the nature and evolution of the galaxies associated with this class of QSO absorbers. Candidate DLA galaxies identified at z </= 1 in the fields of background QSOs show a variety of morphological types without a predominance of spirals. Most properties infer

Cecilia Kozma

We compare model calculations with observations of supernovae at late times to infer the time evolution of temperature, ionization and line emission. Here we mainly report on our results from our modeling of SN 1987A. We discuss the oxygen mass from the modeling of line fluxes. Line profiles show the distribution of the elements and the importance of includi