April 2000 arXiv papers — page 8

Paola Grandi, C. Meg Urry, Laura Maraschi

We briefly review BeppoSAX observations of X-ray bright radio-galaxies. Their X-ray spectra are quite varied, and perhaps surprisingly, any similarity between radio-loud AGN and Seyfert galaxies is the exception rather than the rule. When detected, reprocessing features (iron line and reflection) are generally weak, suggesting two possible scenarios: either:

A. D. Biggs, E. Xanthopoulos, I. W. A. Browne, L. V. E. Koopmans

The complex ten-component gravitational lens system B1933+503 has been monitored with the VLA during the period February to June 1998 with a view to measuring the time delay between the four compact components and hence to determine the Hubble parameter. Here we present the results of an `A' configuration 8.4-GHz monitoring campaign which consists of 37

Evan Scannapieco, Andrea Ferrara, Tom Broadhurst

We show that the gas in growing density perturbations is vulnerable to the influence of winds outflowing from nearby collapsed galaxies that have already formed stars. This suggests that the formation of nearby galaxies with masses less than 10^9 solar masses is likely to be suppressed, irrespective of the details of galaxy formation. An impinging wind may s

Atsushi Taruya, Yasushi Suto

We propose a physical model for nonlinear stochastic biasing of one-point statistics resulting from the formation epoch distribution of dark halos. In contrast to previous works on the basis of extensive numerical simulations, our model provides for the first time an analytic expression for the joint probability function. Specifically we derive the joint pro

P. R. Wozniak, A. Udalski, M. Szymanski, M. Kubiak

In 1998 The Optical Gravitational Lensing Experiment (OGLE) successfully implemented automated data reductions for QSO 2237+0305. Using a new image subtraction method we achieved a differential photometry scatter of 1-5 % for images A-D respectively. Combined with a time sampling of 1-2 times a week this is sufficient for early detection of caustic crossings

Winder A. Moura-Melo, J. A. Helayël-Neto

Classical Maxwell and Maxwell-Chern-Simons (MCS) Electrodynamics in (2+1)D are studied in some details. General expressions for the potential and fields are obtained for both models, and some particular cases are explicitly solved. Conceptual and technical difficulties arise, however, for accelerated charges. The propagation of electromagnetic signals is als

Iosif Bena

In a recent paper, Polchinski and Strassler found a string theory dual of a gauge theory with reduced supersymmetry. Motivated by their approach, we perturb the $\N=8$ theory living on a set of N M2 branes to $\N=2$, by adding fermion mass terms. We obtain M-theory duals corresponding to M2 branes polarized into M5 branes, in $AdS_4 \times S_7$. In the cours

P. R. Berman, B. Dubetsky

A theory of pump-probe spectroscopy is developed in which optical fields drive two-quantum, Raman-like transitions between ground state sublevels. Three fields are incident on an ensemble of atoms. Two of the fields act as the pump field for the two-quantum transitions. The absorption or gain of an additional probe field is monitored as a function of its det

Rutger Vrijen, Eli Yablonovitch

We describe how quantum information may be transferred from photon polarization to electron spin in a semiconductor device. The transfer of quantum information relies on selection rules for optical transitions, such that two superposed photon polarizations excite two superposed spin states. Entanglement of the electron spin state with the spin state of the r

M. Grigorescu

The energy and time variables of the elementary classical dynamical systems are described geometrically, as canonically conjugate coordinates of an extended phase-space. It is shown that the Galilei action of the inertial equivalence group on this space is canonical, but not Hamiltonian equivariant. Although it has no effect at classical level, the lack of e

Carla Figueira de Morisson Faria, Jan-Michael Rost

The order of high harmonics emitted by an atom in an intense laser field is limited by the so-called cutoff frequency. Solving the time-dependent Schrödinger equation, we show that this frequency can be increased considerably by a parabolic confining potential, if the confinement parameters are suitably chosen. Furthermore, due to confinement, the radiation

M. Le Dour, M. Douspis, J. G. Bartlett, A. Blanchard

Using an approximate likelihood method adapted to band--power estimates, we analyze the ensemble of first generation cosmic microwave background anisotropy experiments to deduce constraints over a six--dimensional parameter space describing Inflation--generated adiabatic, scalar fluctuations. The basic preferences of simple Inflation scenarios are consistent

A. E. Koshelev

We calculate the flux-flow resistivity of the Josephson vortex lattice in a layered superconductor taking into account both the inter-plane and in-plane dissipation channels. We consider the limiting cases of small fields (isolated vortices) and high fields (overlapping vortices). In the case of the dominating in-plane dissipation, typical for high-temperatu

G. Barnich, P. A. Grassi

The Caswell-Wilczek analysis on the gauge dependence of the effective action and the renormalization group functions in Yang-Mills theories is generalized to generic, possibly power counting non renormalizable gauge theories. It is shown that the physical coupling constants of the classical theory can be redefined by gauge parameter dependent contributions o

David H. Adams

It is shown that certain global obstructions to gauge-invariance in chiral gauge theory, described in the continuum by Alvarez-Gaume and Ginsparg, are exactly reproduced on the lattice in the Overlap formulation at small non-zero lattice spacing (i.e. close to the classical continuum limit). As a consequence, the continuum anomaly cancellation condition $d_R

Jiliang Jing, Mu-Lin Yan

The covariant phase technique is used to compute the constraint algebra of the stationary axisymmetric charged black hole. A standard Virasoro subalgebra with corresponding central charge is constructed at a Killing horizon with Carlip's boundary conditions. For the Kerr-Newman black hole and the Kerr-Newman-AdS black hole, the density of states determin

Yasunori Nomura, T. Watari, T. Yanagida

Recent cosmological observations suggest the presence of small but nonzero cosmological constant $Λ_{cos}^4 \simeq (2 \times 10^{-3} eV)^4$. It is an intriguing possibility that such a small cosmological constant is supplied by the potential energy density of an ultralight axion-like field (called as quintessence axion). If this axion couples to the electrow

Jesús Salas, Alan D. Sokal

We study the chromatic polynomials (= zero-temperature antiferromagnetic Potts-model partition functions) P_G(q) for m \times n rectangular subsets of the square lattice, with m \le 8 (free or periodic transverse boundary conditions) and n arbitrary (free longitudinal boundary conditions), using a transfer matrix in the Fortuin-Kasteleyn representation. In p

Jerome P. Gauntlett, Gary W. Gibbons, Paul K. Townsend

We argue that MQCD admits intersecting domain walls that are realized as Cayley calibrations of the MQCD M5-brane. We discuss various dual realizations and comment on how branes can realise domain walls in N=1 supersymmetric theories in D=3.

L. Canton, W. Schadow

By considering a class of diagrams which has been overlooked also in the most recent literature on three-body forces, we extract a new contribution to the three-nucleon interaction which specifically acts on the triplet odd states of the two nucleon subsystem. In the static approximation, this 3N-force contribution is fixed by the underlying 2N interaction,

Marco Zoli

A perturbative study of the Holstein Molecular Crystal Model which accounts for lattice structure and dimensionality effects is presented. Antiadiabatic conditions peculiar of narrow band materials and an intermediate to strong electron-phonon coupling are assumed. The polaron effective mass depends crucially in all dimensions on the intermolecular coupling

Marco Zoli

Different classes of physical systems with sizeable electron-phonon coupling and lattice distortions present anomalous resistivity behaviors versus temperature. We study a molecular lattice Hamiltonian in which polaronic charge carriers interact with non linear potentials provided by local atomic fluctuations between two equilibrium sites. We study a molecul

Ruth C. Peterson, Donald M. Terndrup, Elaine M. Sadler, Alistair R. Walker

We present the first results of a survey of blue horizontal branch (BHB) stars in the Galactic bulge. 164 candidates with 15 < V < 17.5 in a field 7.5deg from the Galactic Center were observed in the blue at 2.4A FWHM resolution with the AAT 2dF spectrograph. Radial velocities were measured for all stars. For stars with strong Balmer lines, their profiles we

V. V. Uspenskij

A topological group is minimal if it does not admit a strictly coarser Hausdorff group topology. The Roelcke uniformity (or lower uniformity) on a topological group is the greatest lower bound of the left and right uniformities. A group is Roelcke-precompact if it is precompact with respect to the Roelcke uniformity. Many naturally arising non-Abelian topolo

Stephen L. Adler

The role of probability in quantum mechanics is reviewed, with a discussion of the ``orthodox&#39;&#39; versus the statistical interpretive frameworks, and of a number of related issues. After a brief summary of sources of unease with quantum mechanics, a survey is given of attempts either to give a new interpretive framework assuming quantum mechanics is ex

J. Eisert, M. Wilkens

In these lecture notes we investigate the implications of the identification of strategies with quantum operations in game theory beyond the results presented in [J. Eisert, M. Wilkens, and M. Lewenstein, Phys. Rev. Lett. 83, 3077 (1999)]. After introducing a general framework, we study quantum games with a classical analogue in order to flesh out the peculi

V. V. Dodonov, S. S. Mizrahi, A. L. de Souza Silva

We introduce the quantitative measures characterizing the rates of decoherence and thermalization of quantum systems. We study the time evolution of these measures in the case of a quantum harmonic oscillator whose relaxation is described in the framework of the standard master equation, for various initial states (coherent, `cat&#39;, squeezed and number).

Kh. M. Beshtoev

It is shown, that radiation spectrum of atoms (or nuclei) in the gravitational field has a red shift since the effective mass of radiating electrons (or nucleons) changes in this field. This red shift is equal to the red shift of radiation spectrum in the gravitational field measured in existence experiments. The same shift must arise when the photon (or $ γ

Holger F. Hofmann

Finite resolution quantum nondemolition (QND) measurements allow a determination of light field properties while preserving some of the original quantum coherence of the input state. It is thus possible to measure correlations between the photon number and a quadrature component of the same light field mode. Nonclassical features emerge as photon number quan

Raoul Nakhmanson

Ascribing to inanimate matter a possibility to receive, work on and transfer information allows us to explain quantum-mechanical phenomena including &#34;delayed-choice&#34;- and &#34;Einstein-Podolsky-Rosen (EPR)&#34;-type experiments adhering to the basis of local realism, and to suggest essentially new experiments with microparticles and atoms in which in

Ken Sekimoto, Hatsumi Nakazawa

Biological systems are among the most challenging subjects for theoretical physicists, as well as experimentalists or simulationists. Physical principles should have been both constraints and guide-lines for the evolution of living systems over billions of years. One generally aims at clarifying what physical principles, possibly new ones, are behind the phe

D. Voigt, E. C. Schilder, R. J. C. Spreeuw, H. B. van Linden van den Heuvell

We have characterized a semiconductor amplifier laser system which provides up to 200mW output after a single-mode optical fiber at 780nm wavelength. The system is based on a tapered semiconductor gain element, which amplifies the output of a narrow-linewidth diode laser. Gain and saturation are discussed as a function of operating temperature and injection

Martin Nilsson, Nigel Snoad

In this paper we study the evolution of the mutation rate for simple organisms in dynamic environments. A model with multiple fitness coding loci tracking a moving fitness peak is developed and an analytical expression for the optimal mutation rate is derived. Surprisingly it turns out that the optimal mutation rate per genome is approximately independent of

Alexey K. Mazur

The macroscopic curvature induced in the double helical B-DNA by regularly repeated adenine tracts (A-tracts) is a long known, but still unexplained phenomenon. This effect plays a key role in DNA studies because it is unique in the amount and the variety of the available experimental information and, therefore, is likely to serve as a gate to the unknown ge

Martin Nilsson, Nigel Snoad

A quasispecies evolving on a fitness landscape with a single peak of fluctuating height is studied. In the approximation that back mutations can be ignored, the rate equations can be solved analytically. It is shown that the error threshold on this class of dynamic landscapes is defined by the time average of the selection pressure. In the case of a periodic

Pavel L. Chapovsky

A theoretical model of hyperfine spectra of nuclear spin conversion of molecular isomers has been developed. The model takes into account the nuclear spin-spin and spin-rotation interactions, as well as the saturation of intramolecular mixing of molecular ortho and para states. The model has been applied to hyperfine spectra of nuclear spin conversion in ^{1

A. Yu. Korchin, O. Scholten

Production of lepton pairs in gamma p -> e-e+ p reaction is studied at photon energies up to 1 GeV. We show that even if lepton charge is not measured there are extensive kinematical regimes where the nuclear process dominates over the Bethe-Heitler contribution. The decomposition is performed of the unpolarized cross section for the virtual Compton scatteri

L. Canton, T. Melde, J. P. Svenne

We discuss a working approximation scheme to a recently developed formulation of the coupled piNNN-NNN problem. The approximation scheme is based on the physical assumption that, at low energies, the 2N-subsystem dynamics in the elastic channel is conveniently described by the usual 2N-potential approach, while the explicit pion dynamics describes small, cor

M. Bleicher, A. K. Dutt-mazumder, C. Gale, C. M. Ko

We investigate the baryonic contributions to the dilepton yield in high energy heavy ion collisions within the context of a transport model. The relative contribution of the baryonic and mesonic sources are examined. It is observed that most dominant among the baryonic channels is the decay of N*(1520) and mostly confined in the region below the rho peak. In

W. Reisdorf

We review multifragmentation data obtained at the SIS/GSI accelerator using heavy ion beams with (0.1-1)A GeV together with the ALADIN and FOPI experimental setups.

Ashok Das, Ziemowit Popowicz

In this letter, we study systematically the general properties of the $B$-extension of any integrable model. In addition to discussing the general properties of Hamiltonians, Hamiltonian structures etc, we also clarify the origin of &#34;exotic&#34; charges in such models. We show that, in such models, there exist at least two sets of non-local conserved cha

V. Gafiychuk, I. Lubashevsky, A. Stosyk

We study the emergence of a power law distribution in the systems which can be characterized by a hierarchically organized supplying network. It is shown that conservation laws on the branches of the network can, at some approximation, impose power law properties on the systems. Some simple examples taken from economics, biophysics etc. are considered.

G. Giachetta, L. Mangiarotti, G. Sardanashvily

We study the obstruction to the exactness of the variational complex for a field theory on an affine bundle.

Tetsuya Kikuchi

We study a pair of commuting difference operators arising from the elliptic solution of the dynamical Yang-Baxter equation of type C_2. The operators act on the space of meromorphic functions on the weight space of sp(4,C). We show that these operators can be identified with the system by van Diejen and by Komori-Hikami with special parameters. It turns out

Peter B. Gothen

We consider the moduli spaces of representations of the fundamental group of a surface of genus g greater than 2 in the Lie groups SU(2,2) and Sp(4,R). It is well known that there is a characteristic number of such a representation, whose absolute value is less than or equal to 2g-2. This allows one to write the moduli space as a union of subspaces indexed b

Andrei Okounkov

We prove the conjecture of Baik, Deift, and Johansson which says that with respect to the Plancherel measure on the set of partitions of $n$, the 1st, 2nd, and so on, rows behave, suitably scaled, like the 1st, 2nd, and so on, eigenvalues of a Gaussian random Hermitian matrix as $n$ goes to infinity. Our proof is based on an interplay between maps on surface

Andrei Okounkov

We consider ramified coverings of P^1 with arbitrary ramification type over 0 and infinity and simple ramifications elsewhere and prove that the generating function for the numbers of such coverings is a tau-function for the Toda lattice hierarchy of Ueno and Takasaki.

S. V. Ludkovsky

Diffeomorphism groups $G$ of manifolds $M$ on locally $\bf F$-convex spaces over non-Archimedean fields $\bf F$ are investigated. It is shown that their structure has many differences with the diffeomorphism groups of real and complex manifolds. It is proved that $G$ is not a Banach-Lie group, but it has a neighbourhood $W$ of the unit element $e$ such that

William Pasillas-Lepine, Witold Respondek

We propose in this paper a constructive procedure that transforms locally, even at singular configurations, the kinematics of a car towing trailers into Kumpera-Ruiz normal form. This construction converts the nonholonomic motion planning problem into an algebraic problem (the resolution of a system of polynomial equations), which we illustrate by steering t

William Pasillas-Lepine, Witold Respondek

We give necessary and sufficient geometric conditions for a distribution (or a Pfaffian system) to be locally equivalent to the canonical contact system on Jn(R,Rm), the space of n-jets of maps from R into Rm. We study the geometry of that class of systems, in particular, the existence of corank one involutive subdistributions. We also distinguish regular po

Miguel Abreu

A theorem of Delzant states that any symplectic manifold $(M,\om)$ of dimension $2n$, equipped with an effective Hamiltonian action of the standard $n$-torus $\T^n = \R^{n}/2π\Z^n$, is a smooth projective toric variety completely determined (as a Hamiltonian $\T^n$-space) by the image of the moment map $ϕ:M\to\R^n$, a convex polytope $P=ϕ(M)\subset\R^n$. In

Andrey Todorov

In this paper we generalized the variational formulas for the determinants of the Laplacians on functions of CY metrics to forms of type (0,q) on CY manifolds. We also computed the Ray Singer Analytic torsion on CY manifolds we proved that it is bounded by a constant. In case of even dimensional CY manifolds the Ray Singer Analytic torsion is zero. The inter

Andrey Todorov, Jay Jorgenson

In this article we give a general approach to the following analogue of Shafarevich&#39;s conjecture for some polarized algebraic varieties; suppose that we fix a type of an algebraic variety and look at families of such type of varieties over a fixed Riemann surface with fixed points over which we have singular varieties, then one can ask if the set of such

Yi-Zhi Huang, Antun Milas

We construct the intertwining operator superalgebras and vertex tensor categories for the N=2 superconformal unitary minimal models and other related models.

Edward Goldstein

In the first part of this paper we consider compact algebraic manifolds M^2n with an algebraic (n-1)-Torus action. We show that there is a T-invariant meromorphic section $σ$ of the canonical bundle of M. Any such $σ$ defines a divisor D. On the complement M&#39;=M-D we have a trivialization of the canonical bundle and a T-action. If the first cohomology of

Tomek Bartoszynski, Saharon Shelah

We will show that, consistently, every uncountable set can be continuously mapped onto a non measure zero set, while there exists an uncountable set whose all continuous images into a Polish space are meager.

Washington Taylor

This note focuses on the coupling of a type IIA D2-brane to a background B field. It is shown that the D0-brane charge arising from the integral over the D2-brane of the pullback of the B field is cancelled by bulk contributions, for a compact D2-brane wrapping a homotopically trivial cycle in space-time. In M-theory this cancellation is a straightforward co

Y. Nakawaki, G. McCartor

It is shown that ghost fields are indispensable in deriving well-defined antiderivatives in pure space-like axial gauge quantizations of gauge fields. To avoid inessential complications we confine ourselves to noninteracting abelian fields and incorporate their quantizations as a continuous deformation of those in light-cone gauge. We attain this by construc

Gary McCartor

I shall discuss the regulation of the $P^+ = 0$ singularity and give some examples. Regulating the singularity induces new operators into the theory. This process seems rather different for the case of ultraviolet singularities than for the case of infrared singularities.

Thomas Pisar

We derive the vector supersymmetry and the Ł-symmetry transformations for the fields of a generalized topological $p$-form model of Schwarz-type in $d$ space-time dimensions.

Prasanta Das, Sreerup Raychaudhuri

In models with large extra dimensions, where quantum gravity effects become strong at the TeV scale, the rho-parameter can receive large contributions from one-loop diagrams involving exchange of multiple graviton and dilaton states. These contributions are computed, taking into account cancellation of spurious infrared divergences, and the (finite) results

K. G. Chetyrkin, J. H. Kuehn, M. Steinhauser

In this paper the formulae are collected which are needed for the computation of the strong coupling constant and quark masses at different energy scales and for different number of active flavours. All equations contain the state-of-the-art QCD corrections up to three- and sometimes even four-loop order. For the practical implementation {\tt Mathematica} is

Juan Garcia-Bellido

These notes are intended as an introductory course for experimental particle physicists interested in the recent developments in astrophysics and cosmology. I will describe the standard Big Bang theory of the evolution of the universe, with its successes and shortcomings, which will lead to inflationary cosmology as the paradigm for the origin of the global

Ian Hinchliffe, Aneesh V. Manohar

This paper presents a summary of the current status of determinations of the strong coupling constant alpha_s. A detailed description of the definition, scale dependence and inherent theoretical ambiguities is given. The various physical processes that can be used to determine alpha_s are reviewed and attention is given to the uncertainties, both theoretical

Tran N. Truong

Effective tree Chiral Lagrangian is interpreted as a power series expansion of the kinematical variables. In the presence of the strong interaction this expansion is valid below the unitarity cut, hence in the unphysical region. Consequences of this reinterpretation of the Chiral Lagrangian are analysed for the relation between K-pi and K-pipi transitions.

W. Bernreuther, A. Brandenburg, Z. G. Si

Future hadron collider experiments are expected to record large to huge samples of $t\bar t$ events. The analysis of these data with respect to $t\bar t$ spin-spin correlations requires precise predictions of the production of these quark pairs in a general spin configuration. Therefore we have computed, at next-to-leading order (NLO) in the QCD coupling, th

A. D. Polosa

I review a Constituent-Quark-Meson model (CQM) for heavy meson decays, outlining its characteristics and the calculation techniques developed for it. The strength of this effective model is that it enables to evaluate heavy meson decay amplitudes through diagrams where the heavy mesons are attached at the ends of loops containing heavy and light quark intern

G. Moortgat-Pick, A. Bartl, H. Fraas, W. Majerotto

We study chargino production e^+ e^- -> chi^+_1 chi^-_1 and the subsequent leptonic decay chi^-_1\to chi^0_1 e^- nu_e including the complete spin correlations between production and decay. We work out the advantages of polarizing the e^+ and e^- beams. We study in detail the polarized cross sections, the angular distribution and the forward--backward asymmet

I. V. Kanatchikov

Quantization of general relativity in metric variables using ``precanonical'' quantization based on the De Donder-Weyl covariant Hamiltonian formulation is outlined. Elements of classical geometry needed to formulate the (Dirac-like) wave equation emerge from a self-consistency with the underlying quantum dynamics of the metric. In this sense the formulation

Luis Lehner, Mijan Huq, David Garrison

Causal differencing has shown to be one of the promising and successful approaches towards excising curvature singularities from numerical simulations of black hole spacetimes. So far it has only been actively implemented in the ADM and Einstein-Bianchi 3+1 formulations of the Einstein equations. Recently, an approach closely related to the ADM one, commonly

Sergei M. Kopeikin, Carl R. Gwinn

Attaining the limit of sub-microarcsecond optical resolution will completely revolutionize fundamental astrometry by merging it with relativistic gravitational physics. Beyond the sub-microarcsecond threshold, one will meet in the sky a new population of physical phenomena caused by primordial gravitational waves from early universe and/or different localize

Hongwei Yu, L. H. Ford

The effects of small extra dimensions upon quantum fluctuations of the lightcone are examined. We argue that compactified extra dimensions modify the quantum fluctuations of gravitational field so as to induce lightcone fluctuations. This phenomenon can be viewed as being related to the Casimir effect. The observable manifestation of the lightcone fluctuatio

Deirdre M. Shoemaker, Mijan F. Huq, Richard A. Matzner

We report the development of the first apparent horizon locator capable of finding multiple apparent horizons in a ``generic&#39;&#39; numerical black hole spacetime. We use a level-flow method which, starting from a single arbitrary initial trial surface, can undergo topology changes as it flows towards disjoint apparent horizons if they are present. The le

Alan Coley, Martin Goliath

Closed, spatially homogeneous cosmological models with a perfect fluid and a scalar field with exponential potential are investigated, using dynamical systems methods. First, we consider the closed Friedmann-Robertson-Walker models, discussing the global dynamics in detail. Next, we investigate Kantowski-Sachs models, for which the future and past attractors

Burkhard D. Steinmacher-Burow

Forty years ago Dijkstra introduced the current conventional execution of routines. It places activation frames onto a stack. Each frame is the internal state of an executing routine. The resulting application execution is not easily helped by an external system. This presentation proposes an alternative execution of routines. It places task frames onto the

A. A. Clerk, P. W. Brouwer, V. Ambegaokar

We examine the voltage V and magnetic field B dependent Andreev conductance of a chaotic quantum dot coupled via point contacts to a normal metal and a superconductor. In the case where the contact to the superconductor dominates, we find that the conductance is consistent with the dot itself behaving as a superconductor-- it appears as though Andreev reflec

R. Shrock, F. Y. Wu

The problem of enumerating spanning trees on graphs and lattices is considered. We obtain bounds on the number of spanning trees $N_{ST}$ and establish inequalities relating the numbers of spanning trees of different graphs or lattices. A general formulation is presented for the enumeration of spanning trees on lattices in $d\geq 2$ dimensions, and is applie

M. Vinet, C. Chapelier, F. Lefloch

We investigated the local density of states (LDOS) of a normal metal (N) in good electrical contact with a superconductor (S) as a function of the distance $x$ to the NS interface. The sample consists of a pattern of alternate stripes of Au and Nb made by UV-lithography. We used a low temperature scanning tunneling microscope to record simultaneously $dI/dV(

V. V. Dobrovitski, M. I. Katsnelson, B. N. Harmon

Multiscale phenomena which include several processes occuring simultaneously at different length scales and exchanging energy with each other, are widespread in magnetism. These phenomena often govern the magnetization reversal dynamics, and their correct modeling is important. In the present paper, we propose an approach to multiscale modeling of magnets, a

E. P. Pokatilov, V. M. Fomin, J. T. Devreese, S. N. Balaban

A theory of bipolaron states in quantum wires with a parabolic potential well is developed applying the Feynman variational principle. The basic parameters of the bipolaron ground state (the binding energy, the number of phonons in the bipolaron cloud, the effective mass, and the bipolaron radius) are studied as a function of sizes of the potential well. Two

F. Brosens, J. T. Devreese, L. F. Lemmens

In this addendum we introduce the concept of time-inversion referencing. This is an extension of hypertext allowing authors to cite papers that where not yet published (or even not yet written) when they publish a manuscript. We are convinced that this concept will prove very useful especially when adjustments to the so-called intellectual property rights ha

Ganpathy Murthy

Using a Hamiltonian formulation of Composite Fermions that I recently developed with R. Shankar, I compute the dependence of the spin polarization on the temperature for the translationally invariant fractional quantum Hall states at $ν=1/3$ and $ν=2/5$. I compare my results to experiments at $ν=1/3$ and find reasonably good agreement.

Serge Galam

A new and powerful mean field scheme is presented. It maps to a one-dimensional finite closed chain in an external field. The chain size accounts for lattice topologies. Moreover lattice connectivity is rescaled according to the GM law recently obtained in percolation theory. The associated self-consistent mean-field equation of state yields critical tempera

M. Belesi, G. Papavassiliou, M. Fardis, G. Kallias

139La NMR spin-lattice relaxation rate 1/T1 and rf enhancement experiments provide evidence that the low temperature regime of the ferromagnetic (FM) phase of La1-xCaxMnO3 segregates into highly-conductive and poorly-conductive FM regions, associated with differences in the orbital structure. Remarkably, phase separation is accompanied with the appearance of

Jean Pierre Boon

The automaton known as `Langton&#39;s ant&#39; exhibits a dynamical transition from a disordered phase to an ordered phase where the particle dynamics (the ant) produces a regular periodic pattern (called `highway&#39;). Despite the simplicity of its basic algorithm, Langton&#39;s ant has remained a puzzle in terms of analytical description. Here I show that

J. Salas

We study the dynamic critical behavior of two algorithms: the Swendsen-Wang algorithm for the two-dimensional Potts model with q=2,3,4 and a Swendsen-Wang-type algorithm for the two-dimensional symmetric Ashkin-Teller model on the self-dual curve. We find that the Li--Sokal bound on the autocorrelation time τ_{{\rm int},{\cal E}} \geq const \times C_H is alm

J. H. Jung, H. J. Lee, T. W. Noh, Y. Moritomo

Magnetic field ($H$)-dependent optical conductivity spectra $σ(ω) $ and dielectric constant spectra $ε(ω)$ of a layered antiferromagnet ($A$-type) Pr$_{1/2}$Sr$_{1/2}$MnO$_3$ were presented. At 0.0 T in 4.2 K, the $σ(ω)$ showed a small Drude-like peak in the far-infrared region and a broad absorption peak in the mid-infrared region. With increasing $H$, larg

Ya. M. Blanter, M. E. Raikh

We consider a system of two-dimensional electrons strongly localized by disorder. Interactions create a gap in the average tunneling density of states $ν(E)$ at energies, E, close to the Fermi level. We derive a system of self-consistent equations for the correlators of local densities of occupied and empty states. When either the interactions are screened b

Karl-Peter Marzlin, Weiping Zhang

An extended Bose-Einstein condensate (BEC) in an optical lattice provides a kind of periodic dielectric and causes band gaps to occur in the spectrum of light propagating through it. We examine the question whether these band gaps can modify the spontaneous emission rate of atoms excited from the BEC, and whether they can lead to a self-stabilization of the

Francesca Zambelli, Sandro Stringari

We derive an explicit relationship between the moment of inertia and the quadrupole response function of an interacting gas confined in a harmonic trap. The relationship holds for both Bose and Fermi systems and is well suited to reveal the effects of irrotationality of the superfluid motion. Recent experimental results on the scissors mode are used to extra

Ekkehard Krüger

In part I of this paper a modified BCS mechanism of Cooper pair formation of electrons was proposed. This mechanism is connected with the existence of a narrow, roughly half-filled &#34;superconducting energy band&#34; of given symmetry. The special symmetry of the superconducting band was interpreted within a nonadiabatic extension of the Heisenberg model o

Iwan Jensen, Anthony J Guttmann

Meanders form a set of combinatorial problems concerned with the enumeration of self-avoiding loops crossing a line through a given number of points, $n$. Meanders are considered distinct up to any smooth deformation leaving the line fixed. We use a recently developed algorithm, based on transfer matrix methods, to enumerate plane meanders. This allows us to

Jonathan R. Friedman, Vijay Patel, W. Chen, S. K. Tolpygo

We present experimental evidence for a coherent superposition of macroscopically distinct flux states in an rf-SQUID. When the external flux Phi_x applied to the SQUID is near 1/2 of a flux quantum Phi_0, the SQUID has two nearly degenerate configurations: the zero- and one-fluxoid states, corresponding to a few microamperes of current flowing clockwise or c

Ying Jiang

We present a new generalized topological current in terms of the order parameter field $\vec ϕ$ to describe the topological defect system in O(n) symmetric time-dependent Ginzburg-Landau model. With the aid of the $% ϕ$-mapping method, the structure of the topological defects and the topological quantization of their topological charges in TDGL model are obt

F. S. Guzman, T. Matos, H. Villegas-Brena

An exact, axially symmetric solution to the Einstein-Klein-Gordon field equations is employed to model the dark matter in spiral galaxies. The extended rotation curves from a previous analysis are used to fit the model and a very good agreement is found. It is argued that, although our model possesses three parameters to be fitted, it is better than the non-

L. V. E. Koopmans, A. G. de Bruyn, J. Wambsganss, C. D. Fassnacht

First, we review the current status of the detection of strong `external&#39; variability in the CLASS gravitational B1600+434, focusing on the 1998 VLA 8.5-GHz and 1998/9 WSRT multi-frequency observations. We show that this data can best be explained in terms of radio-microlensing. We then proceed to show some preliminary results from our new multi-frequenc

J. B. Hutchings, R. F. Griffin, F. Menard

Direct imaging of the zeta Cnc system has resolved the fourth star in the system, which is in orbit around zeta Cnc C. The presence of the fourth star has been inferred for many years from irregularities in the motion of star C, and recently from C&#39;s spectroscopic orbit. However, its mass is close to that of C, making its non-detection puzzling. Observin

M. Douspis, J. G. Bartlett, A. Blanchard, M. Le Dour

The majority of present efforts to constrain cosmological parameters with cosmic microwave background (CMB) anisotropy data employ approximate likelihood functions, the time consuming nature of a complete analysis being a major obstacle. We have performed a full (unapproximated) likelihood analysis on several experiments that allows us to examine the various

G. S. Bisnovatyi-Kogan

It is shown that in presence of URCA shell pulsational energy losses due to neutrino emission and nonequilibrium beta heating are much less than energy losses by excitation of short-wavelength acoustic waves. Convective motion in presence of URCA shell is considered, and equations generalizing the mean free path model of convection are derived.

G. P. Rowell, T. Naito, S. A. Dazeley, P. G. Edwards

The atmospheric Cerenkov imaging technique has been used to search for point-like and diffuse TeV gamma-ray emission from the southern supernova remnant, W28, and surrounding region. The search, made with the CANGAROO 3.8m telescope, encompasses a number of interesting features, the supernova remnant itself, the EGRET source 3EG J1800-2338, the pulsar PSR J1