February 2001 arXiv papers — page 7

G. Sardin

An alternative approach to the Standard Model is outlined, being motivated by the increasing theoretical and experimental difficulties encountered by this model, which furthermore fails to be unitary. In particular, the conceptual uneasiness generated by the excessive multiplicity of fundamental elements of the Quark Model, 36 different quarks whose cohesion

D. L. Feng, N. P. Armitage, D. H. Lu, A. Damascelli

The electronic structure of heavily overdoped Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ is investigated by angle-resolved photoemission spectroscopy. The long-sought bilayer band splitting in this two-plane system is observed in both normal and superconducting states, which qualitatively agrees with the bilayer Hubbard model calculations. The maximum bilayer energy spli

A. Meiksin, G. Bryan, M. Machacek

Numerical hydrodynamical simulations are used to predict the expected absorption properties of the Lyman-Alpha forest for a variety of Cold Dark Matter dominated cosmological scenarios: CHDM, OCDM, LCDM, SCDM, and tCDM. Synthetic spectra are constructed duplicating the resolution, signal-to-noise ratio, and wavelength coverage of several published high resol

V. Berezinsky, B. Hnatyk, A. Vilenkin

Cusps of superconducting strings can serve as GRB engines. A powerful beamed pulse of electromagnetic radiation from a cusp produces a jet of accelerated particles, whose propagation is terminated by the shock responsible for GRB. A single free parameter, the string scale of symmetry breaking $η\sim 10^{14} GeV$, together with reasonable assumptions about th

Paul M. B. Vitanyi

We develop a theory of the algorithmic information in bits contained in an individual pure quantum state. This extends classical Kolmogorov complexity to the quantum domain retaining classical descriptions. Quantum Kolmogorov complexity coincides with the classical Kolmogorov complexity on the classical domain. Quantum Kolmogorov complexity is upper bounded

Mariusz P. Dabrowski, Janusz Garecki

We review the canonical superenergy tensor and the canonical angular supermomentum tensors in general relativity and calculate them for space-time homogeneous Gödel universes to show that both of these tensors do not, in general, vanish. We consider both an original dust-filled pressureless acausal Gödel model of 1949 and a scalar-field-filled causal Gödel m

Subir Mukhopadhyay, Koushik Ray

Fractional branes on the non-compact orbifold $\C^3/\Z_5$ are studied. First, the boundary state description of the fractional branes are obtained. The open-string Witten index calculated using these states reproduces the adjacency matrix of the quiver of $\Z_5$. Then, using the toric crepant resolution of the orbifold $\C^3/\Z_5$ and invoking the local mirr

Adam Falkowski, Zygmunt Lalak, Stefan Pokorski

We give the explicit form of the four dimensional effective supergravity action, which describes low energy physics of the Randall-Sundrum model with moduli fields in the bulk and charged chiral matter living on the branes. The relation between 5d and 4d physics is explicit: the low energy action is derived from the compactification of a locally supersymmetr

Timon Boehm, Ruth Durrer, Carsten van de Bruck

We derive dynamical equations to describe a single 3-brane containing fluid matter and a scalar field coupling to the dilaton and the gravitational field in a five dimensional bulk. First, we show that a scalar field or an arbitrary fluid on the brane cannot evolve to cancel the cosmological constant in the bulk. Then we show that the Randall-Sundrum model i

S. M. Bilenky, S. Pascoli, S. T. Petcov

Assuming mixing of three massive Majorana neutrinos, we study the implications of the neutrino oscillation solutions of the solar and atmospheric neutrino problems and of the results of the CHOOZ experiment for the predictions of the effective Majorana mass in neutrinoless double beta decay, |< m >|. The general case of CP-nonconservation is investigated. Th

V. V. Afonin, V. L. Gurevich, R. Laiho

A theory of magnetophonon resonance in quantum wells in a magnetic field tilted to the perpendicular to 2DEG is developed. The resonance is due to the resonant interaction of 2D conduction electrons with the longitudinal optic phonons. The electrons are assumed to be nondegenerate. The angular dependence of the resonant maxima is investigated. The sharpness

Gia Dvali, Alexander Vilenkin

Anthropic solutions to the cosmological constant problem require seemingly unnatural scalar field potentials with a very small slope or domain walls (branes) with a very small coupling to a four-form field. Here we introduce a class of models in which the smallness of the corresponding parameters can be attributed to a spontaneously broken discrete symmetry.

Davoud Kamani

In this paper some properties of the superstring with noncommutative worldsheet are studied. We study the noncommutativity of the spacetime, generalization of the Poincaré symmetry of the superstring, the changes of the metric, antisymmetric tensor and dilaton.

S. Varlamov, G. Seibold

We investigate the structure of the pairing potential in the stripe phase of the two-dimensional Hubbard model. Based on the random phase approximation we discuss in detail the interactions in the charge- and spin channel and compare our calculations with related considerations in commensurate antiferromagnets. Our main finding is that due to the incommensur

M. Urban, M. Buballa, J. Wambach

We present a chirally symmetric hadronic model for the vector and axial-vector correlators in vacuum. The dominant contributions to these correlators come from intermediate pions, rho and a_1 mesons which are calculated in one-loop approximation. The resulting spectral functions are compared with the data obtained by the ALEPH collaboration from tau decay. I

Anindya K. Biswas, Sudipta Mukherji

Recently, Verlinde noted a surprising similarity between Friedmann equation governing radiation dominated universe and Cardy's entropy formula in conformal field theory. In this note, we study a brane-universe filled with radiation and stiff-matter. We analyze Friedmann equation in this context and compare our results with Cardy's entropy formula.

Dongsu Bak, Sung Ku Kim, Kwang-Sup Soh, Jae Hyung Yee

The Chern-Simons theories on a noncommutative plane, which is shown to be describing the quantum Hall liquid, is considered. We introduce matter fields fundamentally coupled to the noncommutative Chern-Simons field. Exploiting BPS equations for the nonrelativistic Chern-Simons theory, we find the exact solutions of multi vortices that are closely packed and

F. Andreozzi, A. Porrino, N. Lo Iudice

We propose a new iterative algorithm for generating a subset of eigenvalues and eigenvectors of large matrices which generalizes the method of optimal relaxations. We also give convergence criteria for the iterative process, investigate its efficiency by evaluating computer storage and time requirements and by a few numerical tests.

Fei Zhou

We study spin correlations in Bose-Einstein condensates of spin 1 bosons with scatterings dominated by a total spin equal 2 channel. We show the low energy spin dynamics in the system can be mapped into an $o(n)$ nonlinear sigma model(NL$σ$M). $n=3$ at the zero magnetic field limit and $n=2$ in the presence of weak magnetic fields. In an ordered phase, the g

Antonio Campos, Carlos F. Sopuerta

We present the results of a systematic investigation of the qualitative behaviour of the Friedmann-Lemaitre-Robertson-Walker (FLRW) and Bianchi I and V cosmological models in Randall-Sundrum brane-world type scenarios.

K. M. Lee, Hao Xu, H. F. Chau

The parity of a bit string of length $N$ is a global quantity that can be efficiently compute using a global counter in ${O} (N)$ time. But is it possible to find the parity using cellular automata with a set of local rule tables without using any global counter? Here, we report a way to solve this problem using a number of $r=1$ binary, uniform, parallel an

D. V. Pakhnin, A. I. Sokolov

For the three-dimensional cubic model, the nonlinear susceptibilities of the fourth, sixth, and eighth orders are analyzed and the parameters δ^(i) characterizing their reduced anisotropy are evaluated at the cubic fixed point. In the course of this study, the renormalized sextic coupling constants entering the small-field equation of state are calculated in

M. A. Sillanpaa, T. T. Heikkila, R. K. Lindell, P. J. Hakonen

We study the electronic density of states in a mesoscopic superconductor near a transparent interface with a ferromagnetic metal. In our tunnel spectroscopy experiment, a substantial density of states is observed at sub-gap energies close to a ferromagnet. We compare our data with detailed calculations based on the Usadel equation, where the effect of the fe

M. P. Anantram

The fundamental question of how chirality affects the electronic coupling of a nanotube to metal contacts is important for the application of nanotubes as nanowires. We show that metallic-zigzag nanotubes are superior to armchair nanotubes as nanowires, by modeling the metal-nanotube interface. More specifically, we show that as a function of coupling streng

Z. Xiong, J. M. Yang

Contributions to the muon anomalous magnetic moment are evaluated in the technicolor model with scalars and topcolor assisted technicolor model. In the technicolor model with scalars, the additional contributions come from the loops of scalars, which were found sizable only for a very large $f/f^{&#39;}$ disfavored by the experiment of $b\to sγ$. The topcolo

Jun Kikuchi, Naohiko Kurata, Kiyoichiro Motoya, Touru Yamauchi

Low-frequency spin dynamics in the S=1/2 antiferromagnetic spin-chain compound α-VO(PO_3)_2 has been studied by means of 31P NMR. The nuclear spin-lattice relaxation rate 1/T_1 at the P site exhibits H^{-1/2} dependence on the applied magnetic field (H) at temperatures (T) well above the intrachain coupling strength J/k_{B} = 3.50 K indicating one-dimensiona

Lam Hui

Conventional Cold Dark Matter cosmological models predict small scale structures, such as cuspy halos, which are in apparent conflict with observations. Several alternative scenarios based on modifying fundamental properties of the dark matter have been proposed. We show that general principles of quantum mechanics, in particular unitarity, imply interesting

A. Ludu, R. F. O&#39;Connell

We provide a simple analytic formula in terms of elementary functions for the Laplace transform j_{l}(p) of the spherical Bessel function than that appearing in the literature, and we show that any such integral transform is a polynomial of order l in the variable p with constant coefficients for the first l-1 powers, and with an inverse tangent function of

S. Gheorghiu-Svirschevski

The author calls attention to previous work with related results, which has escaped scrutiny before the publication of the article &#34;Nonlinear quantum evolution with maximal entropy production&#34;, Phys.Rev.A63, 022105 (2001).

Shahar Dolev, Avshalom C. Elitzur

An experiment is presented in which the alleged progression of a photon&#39;s wave function is ``measured&#39;&#39; by a row of superposed atoms. The photon&#39;s wave function affects only one out of the atoms, regardless of its position within the row, thereby manifesting not only non-local but also non-sequential characteristics. It also turns out that, o

V. A. Bordovitsyn, A. N. Myagkii

The motion of a magnetic spin particle in electromagnetic fields is considered on the basis of general principles of the classical relativistic theory. Alternative approaches in derivation of the equations of charge motion and spin precession, the problem of noncollinearity of the momentum and velocity of a particle with spin, the origin and the meaning of T

V. A. Bordovitsyn, A. N. Myagkii

The structural composition and the properties of the first quantum spin-orientation-dependent correction to synchrotron radiation power are discussed. On the basis of spin mass renormalization it is shown that, in the conventional sence, the Thomas precession is not a source of relativistic radiation. This conclusion is in agreement with well-known statement

V. A. Bordovitsyn, A. N. Myagkii

The problem of the uniqueness in the introduction of spin operators in the synchrotron radiation theory is discussed. For this purpose we give the invariant spin projections on the basis of the spin projections in the rest frame. The spin equations are used to construct the integrals of motion in the presence of the external electromagnetic field.

Massimo Pica Ciamarra

This article is an attempt to generalize the classical theory of reversible computing, principally developed by Bennet [IBM J. Res. Develop., 17(1973)] and by Fredkin and Toffoli [Internat. J. Theoret. Phys., 21(1982)], to the quantum case. This is a fundamental step towards the construction of a quantum computer because a time efficient quantum computation

Ulrich Mohrhoff

According to d&#39;Espagnat we must choose between nonlinear breaks in quantum state evolution and weak objectivity. In this comment it is shown that this choice is forced on us by an inconsistent pseudo-realistic interpretation of quantum states. A strongly objective one-world interpretation of linear quantum mechanics is presented. It is argued that the we

A. Browaeys, A. Robert, O. Sirjean, J. Poupard

We have observed thermalization by elastic collisions of magnetically trapped metastable helium atoms. Our method directly samples the reconstruction of a thermal energy distribution after the application of an RF knife. The relaxation time of our sample towards equilibrium gives an elastic collision rate constant close to the unitarity limit.

P. Pieranski, S. Przybyl

The values of writhe of the most tight conformations, found by the SONO algorithm, of all alternating prime knots with up to 10 crossings are analysed. The distribution of the writhe values is shown to be concentrated around the equally spaced levels. As predicted by Cerf and Stasiak the writhe quantum is shown to be close to the rational 4/7 value. The devi

R. L. Dewar, C. Cuthbert, R. Ball

The spectrum of ideal magnetohydrodynamic (MHD) pressure-driven (ballooning) modes in strongly nonaxisymmetric toroidal systems is difficult to analyze numerically owing to the singular nature of ideal MHD caused by lack of an inherent scale length. In this paper, ideal MHD is regularized by using a $k$-space cutoff, making the ray tracing for the WKB balloo

Felix Naef, Daniel A. Lim, Nila Patil, Marcelo O. Magnasco

One of the most popular tools for large scale gene expression studies are high-density oligonucleotide (GeneChip(R)) arrays. These currently have 16-20 small probe cells (``features&#39;&#39;) for evaluating the transcript abundance of each gene. In addition, each probe is accompanied by a mismatched probe designed as a control for non-specificity. An algori

John Michael Williams

Elementary physical reasoning seems to leave it inevitable that global warming would increase the variability of the weather. The first two terms in an approximation to the global entropy are used to show that global warming has increased the free energy available to drive the weather, and that the variance of the weather should increase correspondingly.

M. Garcon, J. W. Van Orden

A brief review of the history of the discovery of the deuteron in provided. The current status of both experiment and theory for the elastic electron scattering is then presented.

M. Viviani, A. Kievsky, S. Rosati

The Kohn variational principle is formulated for calculating elastic proton-deuteron scattering amplitudes at energies above the deuteron breakup threshold. The use of such a principle with an expansion of the wave function on the (correlated) hyperspherical harmonic basis is discussed.

Michael Murray, BRAHMS Collaboration

For relativistic heavy ion collisions the energy flow in the collision reveals information on the equation of state of matter at high density. The BRAHMS experiment has studied the relation between multipliciity in the sidewards direction and zero degree energy using our Tile Multiplicity Array and Zero Degree Calorimeters. To understand this spectrum requir

Bo-Yu Hou, Wen-Li Yang, Yao-Zhong Zhang, Yi Zhen

The q-deformed supersymmetric t-J model on a semi-infinite lattice is diagonalized by using the level-one vertex operators of the quantum affine superalgebra $U_q[\hat{sl(2|1)}]$. We give the bosonization of the boundary states. We give an integral expression of the correlation functions of the boundary model, and derive the difference equations which they s

A. J. Scott, C. A. Holmes, G. J. Milburn

We introduce three area preserving maps with phase space structures which resemble circle packings. Each mapping is derived from a kicked Hamiltonian system with one of three different phase space geometries (planar, hyperbolic or spherical) and exhibits an infinite number of coexisting stable periodic orbits which appear to `pack&#39; the phase space with c

A. I. Shimabukuro

Standart Coherent State Systems have an analysis based on lattices (von Neumann&#39;s lattices) in terms of wich they are classified, looking at the size of the minimun cell, by: complete, overcomplete and not complete. In this work we analize overcomplete systems with a geometrical viewpoint (holomorphic line-budles). We apply the method to evaluate the deg

A. Sciarrino

Requiring stability of genetic code against translation errors, modelised by suitable mathematical operators in the crystal basis model of the genetic code, the main features of the organisation in multiplets of the mitochondrial and of the standard genetic code are explained.

A. S. Usenko

We obtained a new representation of a solution of the heat conduction equation with boundary condition of the third kind for a layer. The result is presented as a superposition of fundamental solutions for an unbounded system with variable coefficients, the explicit form of which is given. We consider the well-known problem of the evolution of the temperatur

Michael Schlosser

We give multidimensional generalizations of several transformation formulae for basic hypergeometric series of a specific type. Most of the upper parameters of the series differ multiplicatively from corresponding lower parameters by a nonnegative integer power of the base q. In one dimension, formulae for such series have been found, in the q -> 1 case, by

Frederic Chapoton

We define several differential graded operads, some of them being related to families of polytopes : simplices and permutohedra. We also obtain a presentation by generators and relations of the operad K on associahedra introduced in a previous article.

D. Iglesias, J. C. Marrero

We study generalized Lie bialgebroids over a single point, that is, generalized Lie bialgebras. Lie bialgebras are examples of generalized Lie bialgebras. Moreover, we prove that the last ones can be considered as the infinitesimal invariants of Lie groups endowed with a certain type of Jacobi structures. We also propose a method to obtain generalized Lie bi

Sara C. Billey, Gregory S. Warrington

We give an explicit combinatorial description of the irreducible components of the singular locus of the Schubert variety X_w for any element w in S_n. Our description of the irreducible components is computationally more efficient (O(n^6)) than the previously best known algorithms. This result proves a conjecture of Lakshmibai and Sandhya regarding this sin

Jawher El Goul

We prove that the complement of a very generic curve of degree $d$ at least equal to 15 in the projective plane is hyperbolic in the sens of Kobayashi (here, the terminology ``very generic&#39;&#39; refers to complements of countable unions of proper algebraic subsets of the parameter space). We first consider the Dethloff and Lu&#39;s generalisation to the

Francesco Ravanini

The study of Finite Size Effects in Quantum Field Theory allows the extraction of precious perturbative and non-perturbative information. The use of scaling functions can connect the particle content (scattering theory formulation) of a QFT to its ultraviolet Conformal Field Theory content. If the model is integrable, a method of investigation through a nonl

Li-Xin Li

In this paper I present a spacetime of two open universes connected by a Lorentzian wormhole. The spacetime has the following features: (1) It can exactly solve the Einstein equations; (2) The weak energy condition is satisfied everywhere; (3) It has a topology of R^2\times T_g (g\ge 2); (4) It has no event horizons.

Martin Franz Ertl

The constraints of the superfield method in two-dimensional supergravity are adapted to allow for nonvanishing bosonic torsion. As the analysis of the Bianchi identities reveals, a new vector superfield is encountered besides the well-known scalar one. The constraints are solved both with superfields using a special decomposition of the supervielbein, and ex

N. Chepilko, A. Romanenko

Schwinger&#39;s quantization scheme is extended in order to solve the problem of the formulation of quantum mechanics on a space with a group structure. The importance of Killing vectors in a quantization scheme is showed. Usage of these vectors provides algebraic properties of operators to be consistent with the geometrical structure of a manifold. The proc

O. V. Tarasov

A short review of the method for the tensor reduction of Feynman integrals based on recurrence relations with respect to space-time dimension d- is given. A solution of the difference equation with respect to d for the n - point one-loop integrals with arbitrary momenta and masses is presented. The result is written as multiple hypergeometric series dependin

Eric S. Swanson

Hadronic interactions are discussed within the context of the constituent quark model. The &#34;Quark Born Diagram&#34; methodology is outlined, extensive applications to meson-meson and meson-baryon interactions are discussed, and general features of these interactions are highlighted. The second half of this document deals with shortcomings of the quark mo

Robert V. Harlander

Pade approximations appear to be a powerful tool to extend the validity range of expansions around certain kinematical limits and to combine expansions of different limits to a single interpolating function. After a brief outline of the general method, we will review a number of recent applications and describe the modifications that have to be applied in ea

H. P. Nilles, M. Peloso, L. Sorbo

We explicitly calculate nonthermal gravitino production during the preheating period in the inflationary Universe. Contrary to earlier investigations, we consider a two--field model to separate the mechanisms of supersymmetry breaking and inflation. We show that the superpartner of the inflaton is significantly generated, while the gravitino production is co

N. G. Antoniou, F. K. Diakonos, A. S. Kapoyannis

In the vicinity of the quark-hadron critical point, in the phase diagram of QCD, simple power-law relations constrain the mid-rapidity net-baryon density profile, for different heavy-ion processes, in a unifying scheme. The corresponding scaling variable specifies the proximity of a given experiment to the critical point. An important phenomenological aspect

Muneyuki Ishida, Shin Ishida

We investigate the properties of new scalar X_B, X_D and axial-vector X_B*, X_D* mesons, which are recently predicted, in the covariant meson-classification scheme, to exist as the partners of ground-state pseudoscalar B, D and vector B*, D* mesons, respectively, realizing a linear representation of chiral symmetry for the light quark component in heavy-ligh

Andre H. Hoang, Aneesh V. Manohar, Iain W. Stewart

The QCD beta-function and the anomalous dimensions for the Coulomb potential and the static potential first differ at three loop order. We evaluate the three loop ultrasoft anomalous dimension for the Coulomb potential and give the complete three loop running. Using this result, we calculate the leading logarithmic Lamb shift for a heavy quark-antiquark boun

D. Boyanovsky

In these lectures I discuss cosmological phase transitions with the goal of establishing the possibility of observational consequences. I argue that the {\em only} phase transition amenable of experimental study within the foreseeable future is that predicted by QCD and discuss some of the potential observational cosmological consequences associated with thi

The DELPHI Collaboration, P. Abreu

Measurements of the trilinear gauge boson couplings WWgamma and WWZ are presented using the data taken by DELPHI in 1998 at a centre-of-mass energy of 189 GeV and combined with DELPHI data at 183 GeV. Values are determined for Delta(g_1^Z) and Delta(kappa_gamma), the differences of the WWZ charge coupling and of the WWgamma dipole coupling from their Standar

The FOCUS collaboration, J. M. Link

We report the observation of the Cabibbo suppressed decay Ξ_c^+ \to p K^-π^+ using data collected with the FOCUS spectrometer during the 1996--97 Fermilab fixed target run. We find a Ξ_c^+ signal peak of 202\pm35 events. We have measured the relative branching ratios BR(Ξ^+_c\to p K^-π^+)/BR(Ξ^+_c\toΞ^-π^+π^+)= 0.234 \pm 0.047 \pm 0.022 and BR(Ξ^+_c\to p \ba

Reinaldo J. Gleiser, Carlos N. Kozameh

We obtain observational upper bounds on a class of quantum gravity related birefringence effects, by analyzing the presence of linear polarization in the optical and ultraviolet spectrum of some distant sources. In the notation of Gambini and Pullin we find $χ< 10^{-3}$.

Janusz Garecki

Often it is asserted that only by using of the symmetric Landau-Lifschitz energy-momentum complex one is able to formulate a conserved angular momentum complex in General Relativity ({\bf GR}). Obviously, it is an uncorrect statement. For example, years ago, Bergmann and Thomson have given other, very useful expression on angular momentum. This expression is

Jaume Garriga, Alexander Vilenkin

Some of the parameters we call ``constants of Nature&#39;&#39; may in fact be variables related to the local values of some dynamical fields. During inflation, these variables are randomized by quantum fluctuations. In cases when the variable in question (call it $χ$) takes values in a continuous range, all thermalized regions in the universe are statistical

Matej Pavsic, Victor Tapia

Due to the recent renewal in the interest for embedded surfaces we provide a list of commented references of interest.

Marcus Hutter

The provably asymptotically fastest algorithm within a factor of 5 for formally described problems will be constructed. The main idea is to enumerate all programs provably equivalent to the original problem by enumerating all proofs. The algorithm could be interpreted as a generalization and improvement of Levin search, which is, within a multiplicative cons

Ralph Butler, William Gropp, Ewing Lusk

Parallel jobs are different from sequential jobs and require a different type of process management. We present here a process management system for parallel programs such as those written using MPI. A primary goal of the system, which we call MPD (for multipurpose daemon), is to be scalable. By this we mean that startup of interactive parallel jobs comprisi

M. E. Zhitomirsky, T. M. Rice

The power-law temperature dependences of the specific heat, the nuclear relaxation rate, and the thermal conductivity suggest the presence of line nodes in the superconducting gap of Sr2RuO4. These recent experimental observations contradict the scenario of a nodeless (k_x+ik_y)-type superconducting order parameter. We propose that interaction of superconduc

Herbert Schmidt, J. F. Zasadzinski, K. E. Gray, D. G. Hinks

Point-contact tunnel junctions using a Au tip on sintered MgB2 pellets reveal a sharp superconducting energy gap that is confirmed by subsequent metallic Sharvin contacts made on the same sample. The peak in the tunneling conductance and the Sharvin contact conductance follow the BCS form, but the gap values of 4.3 meV are less than the weak-coupling BCS val

Eric J. Friedman, A. S. Landsberg

We study the behavior of two spatially distributed (sandpile) models which are weakly linked with one another. Using a Monte-Carlo implementation of the renormalization group and algebraic methods, we describe how large-scale correlations emerge between the two systems, leading to synchronized behavior.

Adolfo Avella, Ferdinando Mancini, Roland Muenzner

We have investigated the antiferromagnetic phase of the 2D, the 3D and the extended Hubbard models on a bipartite cubic lattice by means of the Composite Operator Method within a two-pole approximation. This approach yields a fully self-consistent treatment of the antiferromagnetic state that respects the symmetry properties of both the model and the algebra

Y. -D. Chuang, A. D. Gromko, A. Fedorov, D. S. Dessau

We present high resolution ARPES data of the bilayer superconductor Bi2Sr2CaCu2O8 (Bi2212) showing a clear doubling of the near EF bands. This splitting approaches zero along the (0,0)-(pi,pi) nodal line and is not observed in single layer Bi2Sr2CuO6 (Bi2201), suggesting that the splitting is due to the long sought after bilayer splitting effect. The splitti

Michael L. Hart, Paul Jefferies, Neil F. Johnson

We present exact analytic results for a new version of the Minority Game (MG) in which strategy performance is recorded over a finite time horizon. The dynamics of this Time Horizon Minority Game (THMG) exhibit many distinct features from the MG and depend strongly on whether the participants are fed real, or random, history strings. The THMG equations are e

C. U. Jung, Min-Seok Park, W. N. Kang, Mun-Seog Kim

We report the effect of the sintering temperature on the superconductivity of MgB2 pellets prepared under a high pressure of 3 GPa. The superconducting properties of the non-heated MgB2 in this high pressure were poor. However, as the sintering temperature increased, the superconducting properties were vastly enhanced, which was shown by the narrow transitio

R. M. L. Evans, C. B. Holmes

Unlike atoms, colloidal particles are not identical, but can only be synthesised within a finite size tolerance. Colloids are therefore polydisperse, i.e. mixtures of infinitely many components with sizes drawn from a continuous distribution. We model the crystallisation of hard-sphere colloids (with/without attractions) from an initially amorphous phase. Th

V. Yu. Irkhin, A. A. Katanin, M. I. Katsnelson

The t-t&#39; Hubbard model for the Fermi level near the Van Hove singularity is considered within the renormalization group and parquet approaches. The interplay of ferromagnetic, antiferromagnetic, and superconducting channels is investigated, and the phase diagram of the model is constructed. In comparison with previous approaches, the account of ferromagn

Mahn-Soo Choi, Rosario Fazio, Jens Siewert, C. Bruder

This paper is devoted to an analysis of the experiment by Nakamura {\it et al.} (Nature {\bf 398}, 786 (1999)) on the quantum state control in Josephson junctions devices. By considering the relevant processes involved in the detection of the charge state of the box and a realistic description of the gate pulse we are able to analyze some aspects of the expe

A. O. Sousa, S. Moss de Oliveira

We combine the Penna Model for biological aging, which is based on the mutation-accumulation theory, with a sort of antagonistic pleiotropy. We show that depending on how the pleiotropy is introduced, it is possible to reproduce both the humans mortality, which increases exponentially with age, and fruitfly mortality, which decelerates at old ages, allowing

G. Misguich, Th. Jolicoeur, S. M. Girvin

The antiferromagnetic Heisenberg model on the frustrated Shastry-Sutherland lattice is studied by a mapping onto spinless fermions carrying one quantum of statistical flux. Using a mean-field approximation these fermions populate the bands of a generalized Hofstadter problem. Their filling leads to the magnetization curve. For SrCu_2(BO_3)_2 we reproduce pla

A. Continenza, S. Picozzi, W. T. Geng, A. J. Freeman

Simple structures of MnX binary compounds, namely hexagonal NiAs and zincblende, are studied as a function of the anion (X = Sb, As, P) by means of the all-electron FLAPW method within local spin density and generalized gradient approximations. An accurate analysis of the structural, electronic and magnetic properties reveals that the cubic structure greatly

Takeo Kato

Quantum nucleation processes in the presence of local moderate inhomogeneities are studied theoretically at high biases. The quantum nucleation rate Gamma is calculated for one-dimensional systems in a form Gamma = A e^(-B/hbar) by using the `bounce&#39; method. The bias-dependence of the exponent B is shown to be changed by inhomogeneities. This change is e

G. Profeta, A. Continenza, A. J. Freeman

We investigate the adsorption of a Ni monolayer on the $β$-SiC(001) surface by means of highly precise first-principles all-electron FLAPW calculations. Total energy calculations for the Si- and C-terminated surfaces reveal high Ni-SiC adsorption energies, with respect to other metals, confirmining the strong reactivity and the stability of the transition me

Paul Ormerod, Laurence Smith

Policy targets are being set increasingly for social and economic variables in the UK. This approach requires that reasonably successful ex ante forecasts can be made. We propose a general methodology for assessing the extent to which this can be done. It has already been applied to GDP growth rate data. In this paper, we illustrate the technique with refere

P Ormerod, C Mounfield

Power law distributions of macroscopic observables are ubiquitous in both the natural and social sciences. They are indicative of correlated, cooperative phenomena between groups of interacting agents at the microscopic level. In this paper we argue that when one is considering aggregate macroeconomic data (annual growth rates in real per capita GDP in the s

F. Schmitt, D. Schertzer, S. Lovejoy

We consider the structure functions S^(q)(T), i.e. the moments of order q of the increments X(t+T)-X(t) of the Foreign Exchange rate X(t) which give clear evidence of scaling (S^(q)(T)~T^z(q)). We demonstrate that the nonlinearity of the observed scaling exponent z(q) is incompatible with monofractal additive stochastic models usually introduced in finance:

T. He, R. J. Cava

The magnetic ground state of perovskite structure CaRuO3 has been enigmatic for decades. Here we show that paramagnetic CaRuO3 can be made ferromagnetic by very small amounts of partial substitution of Ru by Ti. Magnetic hysteresis loops are observed at 5 K for as little as 2% Ti substitution. Ti is non-magnetic and isovalent with Ru, indicating that the pri

José L. Mateos

The problem of the classical deterministic dynamics of a particle in a periodic asymmetric potential of the ratchet type is addressed. When the inertial term is taken into account, the dynamics can be chaotic and modify the transport properties. By a comparison between the bifurcation diagram and the current, we identify the origin of the current reversal as

G. Satta, G. Profeta, F. Bernardini, A. Continenza

We report a detailed study of the electronic and structural properties of the 39K superconductor \mgbtwo and of several related systems of the same family, namely \mgalbtwo, \bebtwo, \casitwo and \cabesi. Our calculations, which include zone-center phonon frequencies and transport properties, are performed within the local density approximation to the densit

R. Mélin

I construct a minimal formalism to describe transport of non separable correlations arising when a superconductor is in contact with several electrodes (being ferromagnetic or normal metal). Transport theory is expressed in terms of effective single site Green&#39;s functions. Part of the circuit is decimated exactly by renormalizing only one physical parame

John P. Hughes

There are a half-dozen or so young supernova remnants in the Magellanic Clouds that display one or more of the following characteristics: high velocity (>1000 km/s) emission, enhanced metallicity, or a rapidly rotating pulsar. I summarize the current state of knowledge of these remnants and present some recent results mostly from the new X-ray astronomy sate

D. Marsden, N. E. White

Anomalous x-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are x-ray sources with unusual properties distinguishing them from both rotation-powered and most accretion-powered pulsars. Using archival ASCA data over the energy range 0.5-10.0 keV, we have studied the spectra of the persistent emission from these sources and their variation with spin-dow

S. S. Larsen, J. P. Brodie, J. P. Huchra, D. A. Forbes

We present a study of globular clusters (GCs) in 17 relatively nearby early-type galaxies, based on deep HST/WFPC2 F555W and F814W images. We compare color distributions, cluster sizes and luminosity functions with those of GCs in the Milky Way. In nearly all cases, a KMM test returns a high confidence level for the hypothesis that a sum of two Gaussians pro

M. A. Malkov, P. H. Diamond

One of the main features of astrophysical shocks is their ability to accelerate particles to extremely high energies. The leading acceleration mechanism, the diffusive shock acceleration is reviewed. It is demonstrated that its efficiency critically depends on the injection of thermal plasma into acceleration which takes place at the subshock of the collisio

Nelson D. Padilla, Manuel E. Merchán, Carlos A. Valotto, Diego G. Lambas

The two-point correlation function is computed for galaxies and groups of galaxies selected using 3-dimensional information from the Updated Zwicky Galaxy Catalog - (UZC). The redshift space distortion of the correlation function $ξ(σ,π)$ in the directions parallel and perpendicular to the line of sight, induced by pairwise group peculiar velocities is evalu