June 2000 arXiv papers — page 8

Paramita Adhya, D. Rai Chaudhuri, Amitava Raychaudhuri

Heavy right-handed neutrinos are of current interest. The interactions and decay of such neutrinos determine their decoupling epoch during the evolution of the universe. This in turn affects various observable features like the energy density, nucleosynthesis, CMBR spectrum, galaxy formation, and baryogenesis. Here, we consider reduction of right-handed elec

Nobuyasu Haga, Sei-ichiro Suga

The NMR relaxation rates of (quasi-)one-dimensional spin gapped systems such as the $S=1/2$ spin ladder with a diagonal interaction and the Haldane-gap system are investigated at low temperatures in magnetic fields. We show that in the regime where the gap is collapsed by magnetic fields, the NMR relaxation rate diverges with decreasing temperature and its e

Michael J. York

Reasonable requirements of (a) physical invariance under particle permutation and (b) physical completeness of state descriptions, enable us to deduce a Symmetric Permutation Rule(SPR): that by taking care with our state descriptions, it is always possible to construct state vectors (or wave functions) that are purely symmetric under pure permutation for all

Hsi-Sheng Goan, G. J. Milburn, H. M. Wiseman, He Bi Sun

We obtain the finite-temperature unconditional master equation of the density matrix for two coupled quantum dots (CQD) when one dot is subjected to a measurement of its electron occupation number using a point contact (PC). To determine how the CQD system state depends on the actual current through the PC device, we use the so-called quantum trajectory meth

Joshua A. Faber, Frederic A. Rasio, Justin B. Manor

Using our new Post-Newtonian SPH (smoothed particle hydrodynamics) code, we study the final coalescence and merging of neutron star (NS) binaries. We vary the stiffness of the equation of state (EOS) as well as the initial binary mass ratio and stellar spins. Results are compared to those of Newtonian calculations, with and without the inclusion of the gravi

W. Dür

We investigate the entanglement properties of multiparticle systems, concentrating on the case where the entanglement is robust against disposal of particles. Two qubits -belonging to a multipartite system- are entangled in this sense iff their reduced density matrix is entangled. We introduce a family of multiqubit states, for which one can choose for any p

S. Mayburov

The quantum measurement problem considered for measuring system (MS) consist of measured state S (particle), detector D and information processing device (observer) O. It's shown that O states selfreference structure results in principal nonobservability of MS interference terms which discriminate pure and mixed S states. Such observables restriction per

Kavita Dorai, Arvind, Anil Kumar

We describe the experimental implementation of a recently proposed quantum algorithm involving quantum entanglement at the level of two qubits using NMR. The algorithm solves a generalisation of the Deutsch problem and distinguishes between even and odd functions using fewer function calls than is possible classically. The manipulation of entangled states of

Tohya Hiroshima

I investigate the decoherence of two-mode squeezed vacuum states by analyzing the relative entropy of entanglement. I consider two sources of decoherence: (i) the phase damping and (ii) the amplitude damping due to the coupling to the thermal environment. In particular, I give the exact value of the relative entropy of entanglement for the phase damping mode

J. R. Mureika

A simple algebraic expression is presented to correct men's and women's 100 metre sprint times for ambient wind and altitude effects. The simplified formula is derived from a more complicated equation of motion used to model the athlete's velocity as a function of time (the velocity curve). This method predicts adjustments to 0-wind and 0-altitud

S. Deser, R. Jackiw, A. P. Polychronakos

We discuss some properties of the intrinsically nonlinear Clebsch decomposition of a vector field into three scalars in d=3. In particular, we note and account for the incompleteness of this parameterization when attempting to use it in variational principles involving Maxwell and Chern-Simons actions. Similarities with string decomposition of metrics and th

I. Lazanu, S. Lazanu, M. Bruzzi

The utilisation of semiconductor materials as detectors and devices operating in high radiation environments, at the future particle colliders, in space applications or in medicine and industry, necessitates to obtain radiation harder materials. A systematic theoretical study has been performed, investigating the interaction of charged hadrons with semicondu

C. Hanhart

Based on a counting scheme for the application of chiral perturbation theory to pion production in NN collisions p-wave production is studied. It is demonstrated that, contrary to the s-wave production where loops enter at too low an order to allow the scheme predictive power, there are certain p-wave observables where parameter free predictions are possible

F. M. Lev, E. Pace, G. Salme`

The deuteron electromagnetic form factors, $A(Q^2)$ and $B(Q^2)$, and the tensor polarization $T_{20}(Q^2)$, are unambiguously calculated within the front-form relativistic Hamiltonian dynamics, by using a novel current, built up from one-body terms, which fulfills Poincaré, parity and time reversal covariance, together with Hermiticity and the continuity eq

M. Baldo, G. F. Burgio, H. -J. Schulze

In the framework of the non-relativistic Brueckner-Bethe-Goldstone theory, we derive a microscopic equation of state for asymmetric and $β$-stable matter containing $Σ^-$ and $Λ$ hyperons. We mainly study the effects of three-body forces (TBFs) among nucleons on the hyperon formation and the equation of state (EoS). We find that, when TBFs are included, the

A. N. Ivanov, H. Oberhummer, N. I. Troitskaya, M. Faber

A dynamics of low-energy nuclear forces is investigated for low-energy electromagnetic and weak nuclear reactions with the deuteron in the Nambu-Jona-Lasinio model of light nuclei by example of the neutron-proton radiative capture (M1-capture) n + p -> D + photon, the photomagnetic disintegration of the deuteron photon + D -> n + p and weak reactions of astr

A. N. Ivanov, H. Oberhummer, N. I. Troitskaya, M. Faber

The probability P(Delta-Delta) to find the Delta-Delta component inside the deuteron, where Delta stands for the Delta(1232) resonance, is calculated in the Nambu-Jona-Lasinio model of light nuclei. We obtain P(Delta-Delta) = 0.3%. This prediction agrees good with the experimental estimate P(Delta-Delta) < 0.4% at 90% of CL (D. Allasia et al., Phys. Lett. B1

A. N. Ivanov, H. Oberhummer, N. I. Troitskaya, M. Faber

The Nambu-Jona-Lasinio model of the deuteron suggested by Nambu and Jona-Lasinio (Phys. Rev. 124 (1961) 246) is formulated from the first principles of QCD. The deuteron appears as a neutron-proton collective excitation, i.e. a Cooper np-pair, induced by a phenomenological local four-nucleon interaction in the nuclear phase of QCD. The model describes the de

R. J. Furnstahl, Brian D. Serot

The underlying philosophy and motivation for quantum hadrodynamics (QHD), namely, relativistic field theories of nuclear phenomena featuring manifest covariance, have evolved over the last quarter century in response to successes, failures, and sharp criticisms. A recent revolution in QHD, based on modern effective field theory and density functional theory

Dmitry E. Pelinovsky, Yuri S. Kivshar

We obtain the most general matrix criterion for stability and instability of multi-component solitary waves considering a system of $N$ incoherently coupled nonlinear Schrodinger equations. Soliton stability is studied as a constrained variational problem which is reduced to finite-dimensional linear algebra. We prove that unstable (all real and positive) ei

F. Toschi, E. Leveque, G. Ruiz-Chavarria

Motivated by recent experimental and numerical results, a simple unifying picture of intermittency in turbulent shear flows is suggested. Integral Structure Functions (ISF), taking into account explicitly the shear intensity, are introduced on phenomenological grounds. ISF can exhibit a universal scaling behavior, independent of the shear intensity. This pic

Apoloniusz Tyszka

Let Q denote the field of rational numbers. Let F \subseteq R is a euclidean field. We prove that: (1) if x,y \in F^n (n>1) and |x-y| is constructible by means of ruler and compass then there exists a finite set S(x,y) \subseteq F^n containing x and y such that each map from S(x,y) to R^n preserving unit distance preserves the distance between x and y, (2) i

Zhan Shi, Balint Toth

We survey the current status of the list of questions related to the favourite (or: most visited) sites of simple random walk on Z, raised by Pal Erdos and Pal Revesz in the early eighties.

Alex Eskin, Andrei Okounkov

We compute the asymptotics of the number of connected branched coverings of a torus as their degree goes to infinity and the ramification type stays fixed. These numbers are equal to the volumes of the moduli spaces of pairs (curve, holomorphic differential) with fixed multiplicities of zeros of the differential and have several applications in ergodic theor

J. Wildeshaus

The main purpose of this paper is the geometric construction, and the analysis of the formalism of elliptic Bloch groups. In the setting of absolute cohomology, we obtain a generalization of Beilinson&#39;s Eisenstein symbol to divisors of an elliptic curve, whose support is not necessarily torsion. For motivic cohomology, such a generalization is obtained i

Ruy Exel, Marcelo Laca

Given a countably infinite 0-1 matrix A without identically zero rows, let O_A be the Cuntz-Krieger algebra recently introduced by the authors and T_A be the Toeplitz extension of O_A, once the latter is seen as a Cuntz-Pimsner algebra, as recently shown by Szymanski. We study the KMS equilibrium states of C*-dynamical systems based on O_A and T_A, with dyna

Anton Alekseev, Yvette Kosmann-Schwarzbach, Eckhard Meinrenken

A quasi-Poisson manifold is a G-manifold equipped with an invariant bivector field whose Schouten bracket is the trivector field generated by the invariant element in $\wedge^3 \g$ associated to an invariant inner product. We introduce the concept of the fusion for such manifolds, and we relate quasi-Poisson manifolds to the previously introduced quasi-Hamil

Y. Brihaye, E. Kowalczyk, P. Maslanka

The complete list of Poisson-Lie structures on 4-d Galilei group is presented.

Hajime Tsuji

This is a sequal paper to math.AG/9909021. By using the theory of AZD originated by the author, I prove that for every smooth projective $n$-fold $X$ of general type and every \[ m\geq \lceil\sum_{\ell =1}^{n}\sqrt[\ell]{2} \ell\rceil +1, \] $\mid mK_{X}\mid$ gives a birational rational map from $X$ into a projective space, unless it has a nontrivial (relati

Boris Tsirelson

Stationary Gaussian generalized random processes having slowly decreasing spectral densities give rise to product systems in the sense of William Arveson (basically, continuous tensor product systems of Hilbert spaces). A continuum of nonisomorphic unitless product systems is produced, answering a question of Arveson.

Allan Donsig, Alan Hopenwasser, David R. Pitts

Kadison&#39;s transitivity theorem implies that, for irreducible representations of C*-algebras, every invariant linear manifold is closed. It is known that CSL algebras have this propery if, and only if, the lattice is hyperatomic (every projection is generated by a finite number of atoms). We show several other conditions are equivalent, including the cond

Nicola Grillo

One-loop calculations in quantum gravity coupled to U(1)-Abelian fields (photon fields) are ultraviolet finite and cutoff-free in the framework of causal perturbation theory. We compute the photon loop correction to the graviton propagator and the photon self-energy in second order perturbation theory. Perturbative gauge invariance to second order is shown a

Nicola Grillo

In this paper we show that the one-loop graviton self-energy contribution is ultraviolet finite, without introducing counterterms, and cutoff-free in the framework of causal perturbation theory. In addition, it satisfies the gravitational Slavnov-Ward identities for the two-point connected Green function. The condition of perturbative gauge invariance to sec

Nicola Grillo

In this paper we lay the foundations of causal quantum gravity (CQG), i.e. of a quantum theory of self-interacting symmetric massless rank-2 tensor gauge fields, the gravitons, on flat space-time, in the framework of causal perturbation theory. The causal inductive construction of the S-matrix for quantum gravity leads to a very satisfactory treatment of the

Yuji Igarashi, Katsumi Itoh, Hiroto So

Using the average action defined with a continuum analog of the block spin transformation, we show the presence of gauge symmetry along the Wilsonian renormalization group flow. As a reflection of the gauge symmetry, the average action satisfies the quantum master equation(QME). We show that the quantum part of the master equation is naturally understood onc

S. T. Tsou

Gauge theory, which is the basis of all particle physics, is itself based on a few fundamental concepts, the consequences of which are often as beautiful as they are deep. In this short lecture course I shall try to give an introduction to these concepts, both from the physical and mathematical points of view. Then I shall show how these considerations lead

Robert Marnelius

The BRST-antiBRST invariant path integral formulation of classical mechanics of Gozzi et al is generalized to pseudomechanics. It is shown that projections to physical propagators may be obtained by BRST-antiBRST invariant boundary conditions. The formulation is also viewed from recent group theoretical results within BRST-antiBRST invariant theories. A natu

Robert Marnelius, Niclas Sandstrom

Any regular quantum mechanical system may be cast into an abelian gauge theory by simply reformulating it as a reparametrization invariant theory. We present a detailed study of the BRST quantization of such reparametrization invariant theories within a precise operator version of BRST. The treatment elucidates several intricate aspects of the BRST quantizat

Carlos Pinheiro, F. C. Khanna

The cosmological term is assumed to be a function of time such as $Λ=Ba^{-2}$ where a(t) means the scale factor of standard cosmology. Analytical solutions for radiation dominated epoch and open universe are found. For closed universe, k=+1, and for flat universe, k=0, we show a numerical solution. In general the scenario of Big Bang is preserved in our case

Carlos Pinheiro, F. C. Khanna

We propose a topological Chern-Simons term in D=5 dimensions coupled to Einstein Hilbert theory. Hartree approximation for topological Lagrangian and the Chern-Simons term in D=3 is considered. An effective model of Quantum Gravity in D=5 dimensions is presented here. The analysis of residues is considered and the unitarity is guaranteed at tree level. The p

Sebastian Jaimungal, Ariel R. Zhitnitsky

A novel Coulomb gas (CG) description of low energy $QCD_4$, based on the dual transformation of the QCD effective chiral Lagrangian, is constructed. The CG is found to contain several species of charges, one of which is fractionally charged and can be interpreted as instanton-quarks. The creation operator which inserts a pseudo-particle in the CG picture is

Matthias Neubert

We review recent advances in the theory of strong-interaction effects and final-state interactions in hadronic weak decays of heavy mesons. In the heavy-quark limit, the amplitudes for most nonleptonic, two-body B decays can be calculated from first principles and expressed in terms of semileptonic form factors and light-cone distribution amplitudes. We disc

Duane A. Dicus, Wayne W. Repko, Roberto Vega

We compute the cross section for neutrino-photon scattering taking into account a neutrino mass. We explore the possibility of using intense neutrino beams, such as those available at proposed muon colliders, together with high powered lasers to probe the neutrino mass in photon-neutrino collisions.

W. Schaefer

Starting from the phenomenologically successful color dipole representation of the diffractive structure function, we identify the dominant contribution to the diffractive cross section at small beta. The beta dependence is calculated taking advantage of the Regge factorization properties of the hard mechanism which drives the dependence on the diffractive m

K. Huitu, J. Laitinen, J. Maalampi, N. Romanenko

We consider the production of singly charged Higgs bosons in the Higgs triplet and two Higgs doublet models. We evaluate the cross sections for the pair production and the single production of charged higgses at linear collider. The decay modes of $H^+$ and the Standard Model backgrounds are considered. We analyze the possibilities to differentiate between t

J. Pasupathy

The assumption that the ratio of the Higgs self-coupling to the square of its yukawa coupling to the top is (almost) independent of the renormalization scale fixes the Higgs mass within narrow limits at m=160 GeV using only the values of gauge couplings and top mass.

Harald P. Pfeiffer, Saul A. Teukolsky, Gregory B. Cook

Using an effective potential method we examine binary black holes where the individual holes carry spin. We trace out sequences of quasi-circular orbits and locate the innermost stable circular orbit as a function of spin. At large separations, the sequences of quasi-circular orbits match well with post-Newtonian expansions, although a clear signature of the

Michael Tsamparlis, Pantelis S. Apostolopoulos

All diagonal proper Bianchi I space-times are determined which admit certain important symmetries. It is shown that for Homotheties, Conformal motions and Kinematic Self-Similarities the resulting space-times are defined explicitly in terms of a set of parameters whereas Affine Collineations, Ricci Collineations and Curvature Collineations, if they are admit

Simonetta Frittelli, Roberto Gomez

It is shown that the formulation of the Einstein equations widely in use in numerical relativity, namely, the standard ADM form, as well as some of its variations (including the most recent conformally-decomposed version), suffers from a certain but standard type of ill-posedness. Specifically, the norm of the solution is not bounded by the norm of the initi

Roberto Gomez, Philippos Papadopoulos, Jeffrey Winicour

We present the details of an algorithm for the global evolution of asymptotically flat, axisymmetric spacetimes, based upon a characteristic initial value formulation using null cones as evolution hypersurfaces. We identify a new static solution of the vacuum field equations which provides an important test bed for characteristic evolution codes. We also sho

L. Herrera, J. L. Hernandez Pastora

We calculate the precession of a gyroscope at rest in a Bondi spacetime. It is shown that, far from the source, the leading term in the rate of precession of the gyroscope is simply expressed through the news function of the system, and vanishes if and only if there is no news. Rough estimates are presented, illustrating the order of magnitude of the expecte

Ken-ichi Nakao, Tomohiro Harada, Masaru Shibata, Seiji Kawamura

We rigorously analyze the frequency response functions and antenna sensitivity patterns of three types of interferometric detectors to scalar mode of gravitational waves which is predicted to exist in the scalar-tensor theory of gravity. By a straightforward treatment, we show that the antenna sensitivity pattern of the simple Michelson interferometric detec

David J. Bergman, David G. Stroud

The self consistent effective medium approximation (SEMA) is used to study three-dimensional random conducting composites under the influence of a strong magnetic field {\bf B}, in the case where all constituents exhibit isotropic response. Asymptotic analysis is used to obtain almost closed form results for the strong field magnetoresistance and Hall resist

A. Zheludev, S. Maslov, T. Yokoo, J. Akimitsu

Of great recent interest in condensed matter physics are phenomena of coexistence of quantum and classical properties in the same material. Such duality occurs in certain mixed-spin antiferromagnets composed of quantum spin chains interacting through ``auxiliary&#39;&#39; magnetic ions. In this category are linear-chain rare earth nickelates that exhibit a s

Diego A. R. Dalvit, Jacek Dziarmaga, Wojciech H. Zurek

We consider quantum superposition states in Bose-Einstein condensates. A decoherence rate for the Schrödinger cat is calculated and shown to be a significant threat to this macroscopic quantum superposition of BEC&#39;s. An experimental scenario is outlined where the decoherence rate due to the thermal cloud is dramatically reduced thanks to trap engineering

Lorenz Bartosch, Peter Kopietz

In the pseudogap regime of one-dimensional incommensurate Peierls systems, fluctuations of the phase of the order parameter prohibit the emergence of long-range order and generate a finite correlation length. For classical phase fluctuations, we present exact results for the average electronic density of states, the mean localization length, the electronic s

Lorenz Bartosch, Peter Kopietz

We present an exactly solvable toy model which describes the emergence of a pseudogap in an electronic system due to a fluctuating off-diagonal order parameter. In one dimension our model reduces to the fluctuating gap model (FGM) with a gap Delta (x) that is constrained to be of the form Delta (x) = A e^{i Q x}, where A and Q are random variables. The FGM w

N. S. Branco, J. R. de Sousa

In this work we apply two different real-space renormalization-group (RSRG) approaches to the anisotropic antiferromagnetic spin-1/2 Heisenberg model on the square lattice. Our calculations allow for an approximate evaluation of the $T$ vs. $Δ$ phase-diagram: the results suggest the existence of a critical value of $Δ>0$, at which the critical temperature go

M. Nishiyama, T. Morimoto, S. Maegawa, T. Inami

Jarosite family compounds, KFe_3(OH)_6(SO_4)_2, (abbreviate Fe jarosite), and KCr_3(OH)_6(SO_4)_2, (Cr jarosite), are typical examples of the Heisenberg antiferromagnet on the kagome lattice and have been investigated by means of magnetization and NMR experiments. The susceptibility of Cr jarosite deviates from Curie-Weiss law due to the short-range spin cor

A. Zee, Ian Affleck

Euclidean random matrices appear in a broad class of physical problems involving disorder. The problem of determining their spectra can be mapped, using the replica method, into the study of a scalar field theory with an interaction of the type e^(psi^2). We apply the instanton method to study their spectral tails.

G. Alvarez, H. Fort

The Landau-Ginzburg-Wilson hamiltonian is studied for different values of the parameter $λ$ which multiplies the quartic term (it turns out that this is equivalent to consider different values of the coherence length $ξ$ in units of the lattice spacing $a$). It is observed that amplitude fluctuations can change dramatically the nature of the phase transition

D. S. Petrov, G. V. Shlyapnikov, J. T. M. Walraven

We discuss the regimes of quantum degeneracy in a trapped 1D gas and obtain the diagram of states. Three regimes have been identified: the BEC regimes of a true condensate and quasicondensate, and the regime of a trapped gas of Tonks (gas of impenetrable bosons). The presence of a sharp cross-over to the BEC regime requires extremely small interaction betwee

I. S. Beloborodov, K. B. Efetov, Alexander Altland, F. W. J. Hekking

We study the electronic properties of an array of small metallic grains connected by tunnel junctions. Such an array serves as a model for a granular metal. Previous theoretical studies of junction arrays were based on models of quantum dissipation which did not take into account the diffusive motion of electrons within the grains. We demonstrate that these

Anthony P. Roberts, Edward J. Garboczi

The finite element method (FEM) is used to study the influence of porosity and pore shape on the elastic properties of model porous ceramics. The Young&#39;s modulus of each model was found to be practically independent of the solid Poisson&#39;s ratio. At a sufficiently high porosity, the Poisson&#39;s ratio of the porous models converged to a fixed value i

H. Hünnefeld, T. Niemöller, J. R. Schneider, B. A. Kaufmann

The critical fluctuations in SrTiO$_3$ near its $105 K$ structural phase transition were studied with triple axis diffractometry using high energy ($\ge 100 keV$) synchrotron radiation in different SrTiO$_3$ crystals with different oxygen vacancy concentrations. Due to the presence of oxygen vacancies the critical behaviour is changed compared to defect-free

Merav Opher, Reuven Opher

The fluctuation-dissipation theorem is used to evaluate the screening factor of nuclear reactions due to the electromagnetic fluctuations in a plasma. We show that the commonly used Saltpeter factor is obtained if only fluctuations near the plasma eigenfrequency are assumed to be important (ω\sim ω_{pe}\ll T (\hbar=k_{B}=1)). By taking into account all the f

Jay Anderson, Ivan R. King

The first step toward doing high-precision astrometry is the measurement of individual stars in individual images, a step that is fraught with dangers when the images are undersampled. The key to avoiding systematic positional error in undersampled images is to determine an extremely accurate point-spread function (PSF). We apply the concept of the {\it effe

B. Kliem, M. Karlicky, A. O. Benz

Decimetric radio observations of the impulsive solar flare on October 5, 1992, 09:25 UT show a long series of quasi-periodic pulsations deeply modulating a continuum in the 0.6-2 GHz range that is slowly drifting toward lower frequencies. We propose a model in which the pulsations of the radio flux are caused by quasi-periodic particle acceleration episodes

Mordecai-Mark Mac Low

Numerical models of the dynamical interstellar medium show that interactions between structures such as supernova remnants and superbubbles are more important than the structures themselves in determining the behavior of the ISM. I review the techniques and conclusions of recent global models, focussing on what they tell us about the formation of star-formin

Mark B. Hoffman, Michael S. Turner

The observables $T/S$ and $n-1$ are key to testing and understanding inflation. ($T$, $S$, and $n-1$ respectively quantify the gravity-wave and density-perturbation contributions to CMB anisotropy and the deviation of the density perturbations from the scale-invariant form.) Absent a standard model, there is no definite prediction for, or relation between, $

T. W. Murphy, B. T. Soifer, K. Matthews, L. Armus

Near-infrared spectroscopy using the new Palomar Integral Field Spectrograph indicates the presence of an AGN (active galactic nucleus) in the ultraluminous infrared galaxy IRAS 08311-2459. The high-velocity wings of the Paschen-alpha hydrogen recombination line are seen to be spatially unresolved, and with no positional offset between red and blue high velo

Pawan Kumar, Alin Panaitescu

We calculate the {\it afterglow} emission for Gamma-Ray Bursts (GRBs) going off in an extremely low density medium, referred to as {\it naked bursts}. Our results also apply to the case where the external medium density falls off sharply at some distance from the burst. The observed afterglow flux in this case originates at high latitudes, i.e. where the ang

Adrian Dumitru, Miklos Gyulassy

The evolution of the gluon plasma produced with saturation initial conditions is calculated via transport theory for nuclear collisions with 0.1 <sqrt(s) <10 A TeV. The effective longitudinal pressure is found to remain significantly below the lattice QCD pressure with these initial conditions until the plasma cools to near the confinement scale. The absolut

D. A. R. Dalvit, J. Dziarmaga, W. H. Zurek

When part of the environment responsible for decoherence is used to extract information about the decohering system, the preferred {\it pointer states} remain unchanged. This conclusion -- reached for a specific class of models -- is investigated in a general setting of conditional master equations using suitable generalizations of predictability sieve. We a

S. E. Savel'ev, Guillermo Ramirez-Santiago

We have investigated analitycally the phase diagram of a generalized spherical version of the Blume-Emery-Griffiths model that includes ferromagnetic or antiferromagnetic spin interactions as well as quadrupole interactions in zero and nonzero magnetic field. We show that in three dimensions and zero magnetic field a regular paramagnetic-ferromagnetic (PM-FM

Jaume Gomis, Thomas Mehen, Mark B. Wise

We study field theories on spaces with additional compact noncommutative dimensions. As an example, we study ϕ^3 on R^{1,3}\times T^{2}_θusing perturbation theory. The infrared divergences in the noncompact theory give rise to unusual dynamics for the mode of ϕwhich is constant along the torus. Correlation functions involving this mode vanish. Moreover, we s

J. L. Boldo, C. A. G. Sasaki, S. P. Sorella, L. C. Q. Vilar

The vector supersymmetry of the 2D topological BF model is extended to 2D Yang-Mills. The consequences of the corresponding Ward identity on the ultraviolet behavior of the theory are analyzed.

Bogdan Mihaila, Fred Cooper, John F. Dawson

In this paper we discuss two methods of resumming the leading and next to leading order in 1/N diagrams for the quartic O(N) model. These two approaches have the property that they preserve both boundedness and positivity for expectation values of operators in our numerical simulations. These approximations can be understood either in terms of a truncation t

Ernest Ma, Martti Raidal

We consider the radiative decay b \to s γin a supersymmetric extension of the standard model of particle interactions, where the $b$-quark mass is entirely radiative in origin. This is accomplished by the presence of nonholomorphic soft supersymmetry breaking terms in the Lagrangian. As a result, the contributions to the b \to s γamplitude from the charged H

Liliana Gomez, Ariel Dobry, Hung Diep

We study in this paper the melting transition of a crystal of fcc structure with the Lennard-Jones potential, by using isobaric-isothermal Monte Carlo simulations. Local and collective updates are sequentially used to optimize the convergence. We show the important role played by defects in the melting mechanism in favor of modern melting theories.

G. Duplancic, B. Nizic

Using the Feynman parameter method, we have calculated in an elegant manner a set of one$-$loop box scalar integrals with massless internal lines, but containing 0, 1, 2, or 3 external massive lines. To treat IR divergences (both soft and collinear), the dimensional regularization method has been employed. The results for these integrals, which appear in the

Fernando Sols, Mathias Wagner

The use of a band offset between the two leads of an electron pump driven by a local oscillating voltage is shown to increase the pump current dramatically. The structure of the electron transmission suggests the existence of dominant inelastic channels which we call pipelines. This permits the formulation of a simple model that gives a physical account of t

S. Gardner, G. Valencia

We consider the impact of isospin violation on the analysis of K-> pi pi decays. We scrutinize, in particular, the phenomenological role played by the additional weak amplitude, of |Delta I|=5/2 in character, incurred by the presence of isospin violation. We show that Watson&#39;s theorem is appropriate in O(m_d-m_u), so that the inferred pi-pi phase shift a

J. Golak, H. Kamada, H. Witała, W. Gloeckle

pd capture processes at various energies have been analyzed based on solutions of 3N-Faddeev equations and using modern NN forces. The application of the Siegert theorem is compared to the explicit use of $π$- and $ρ$-like exchange currents connected to the AV18 NN interaction. Overall good agreement with cross sections and spin observables has been obtained

Annamaria Panza, Roberto Soldati

It is shown, by explicit calculation in the axial gauge, that the renormalization group flow for the Wilson loop in perturbation theory does exhibit singularities and consequently it can not eventually reproduce the gauge invariant result, when the infrared cut off is removed

D. C. Cabra, A. Lopez, G. L. Rossini

We study the transition from the Abelian multi-component (3,3,1) quantum Hall state to the non-Abelian one component Pfaffian state in bilayer two dimensional electron systems. We show that tunneling between layers can induce this transition. At the transition points part of the degrees of freedom that describe the (3,3,1) state disappear from the spectrum,

Ann E. Nelson, Matthew J. Strassler

We present a new mechanism, which does not require any flavor symmetry, to explain the small Yukawa couplings and CKM mixing angles. The Yukawa matrices are assumed to be random at short distances and the hierarchical structure is generated in the infrared by renormalization group flow. The generic qualitative predictions of this mechanism are in good agreem

Chao-Shang Huang, LIAO Wei, Qi-Shu Yan, Shou-Hua Zhu

In this paper we analyze the process $B_s \to \ell^+ \ell^-$ in a model II 2HDM and MSSM. All the leading terms of Wilson coefficients relevant to the process are given in the large tan$β$ limit. It is shown that the decay width for $B_s \to \ell^+ \ell^-$ depends on all parameters except $m_{A^0}$ in the 2HDM. The branching ratio of $B_s \to μ^+ μ^-$ can re

David Berenstein, Vishnu Jejjala, Robert G. Leigh

We review and extend recent work on the application of the non-commutative geometric framework to an interpretation of the moduli space of vacua of certain deformations of N=4 super Yang-Mills theories. We present a simple worldsheet calculation that reproduces the field theory results and sheds some light on the dynamics of the D-brane bubbles. Different re

E. Cappelluti, C. Grimaldi, L. Pietronero, S. Straessler

High-$T_c$ superconductors are characterized by very low carrier densities. This feature leads to two fundamental consequences: on one hand the Fermi energies are correspondingly small and they can be of the same order of phonon frequencies. In such a situation nonadiabatic corrections arising from the breakdown of Migdal&#39;s theorem can not be longer negl

P. P. Avelino, C. J. A. P. Martins

We extend our recent work on ``two-metric&#39;&#39; theories of gravity by showing how in such models cosmic defects can produce a spectrum of primordial Gaussian density perturbations. This will happen when the speed characterising the decay products of the defect network is much larger than the speed characterising gravity and all standard model particles.

G. D&#39;Anna, G. Gremaud

The quasi-static frequency response of a granular medium is measured by a forced torsion oscillator method, with forcing frequency $f_{p}$ in the range $10^{-4}$ Hz to 5 Hz, while weak vibrations at high-frequency $f_{s}$, in the range 50 Hz to 200 Hz, are generated by an external shaker. The intensity of vibration, $Γ$, is below the fluidization limit. A lo

Peter Hasenfratz, Ferenc Niedermayer

We study the behavior of asymptotically free (AF) spin and gauge models when their continuous symmetry group is replaced by different discrete non-Abelian subgroups. Precise numerical results with relative errors down to O(0.1%) suggest that the models with large subgroups are in the universality class of the underlying original models. We argue that such a

G. Brandenburg, CLEO Collaboration

Using 13.4 $fb^{-1}$ of data collected with the CLEO detector at the Cornell Electron Storage Ring, we have observed 300 events for the two-photon production of ground-state pseudo-scalar charmonium in the decay $η_c$ -> $K_S K^{\mp} π^{\pm}$. We have measured the $η_c$ mass to be (2980.4 +- 2.3 (stat) +- 0.6 (sys)) MeV and its full width as (27.0 +- 5.8 (st

Matthias Brack

We investigate the isochronous bifurcations of the straight-line librating orbit in the Henon-Heiles and related potentials. With increasing scaled energy e, they form a cascade of pitchfork bifurcations that cumulate at the critical saddle-point energy e=1. The stable and unstable orbits created at these bifurcations appear in two sequences whose self-simil

Bora Orcal, Ayse Erzan

We study the temporal and spatial correlations in a one-dimensional model of a heterogeneous fault zone, in the presence of visco-elastic effects. As a function of dynamical weakening and of dissipation, the system exhibits three different &#34;phases&#34; : one in which there are no time correlations between the events, a second, in which there are ``Omori&

Luca Amendola

The recent high-quality Boomerang data allow to test many competing cosmological models. Here I present a seven-parameter likelihood analysis of dark energy models with exponential potential and explicit coupling to dark matter. Such a model is conformally equivalent to a scalar field with non-minimal coupling to gravity. So far, the constraints on a dark en

P. Caldiroli, R. Musina

We prove existence of S^2-type parametric surfaces in R^3 having prescribed noncostant mean curvature.

A. de Visser, M. J. Graf, P. Estrela, A. Amato

Transverse-field muon spin relaxation measurements have been carried out on the heavy-fermion superconductor UPt3 doped with small amounts of Pd. We find that the critical Pd concentration for the emergence of the large-moment antiferromagnetic phase is ~0.6 at.%Pd. At the same Pd content, superconductivity is completely suppressed. The existence of a magnet

A. Bednorz, M. Napiorkowski

In the reduced one-dimensional description of the adsorption on the wedge-shaped substrate the mid-point interface height serves as the order parameter. We point at the ambiguity which appears in the transfer-matrix approach to this problem. We also propose how to avoid this problem by introducing the appropriate order parameter.