December 1998 arXiv papers — page 20

R. D. Blum, A. Damineli, P. S. Conti

Near infrared images of the Galactic giant HII region W43 reveal a dense stellar cluster at its center. Broad band JHK photometry of the young cluster and K-band spectra of three of its bright stars are presented. The 2 micron spectrum of the brightest star in the cluster is very well matched to the spectra of Wolf-Rayet stars of sub-type WN7. Two other star

G. De Zotti, L. Toffolatti

We discuss the main uncertainties affecting estimates of small scale fluctuations due to extragalactic sources in the Planck Surveyor frequency bands. Conservative estimates allow us to confidently conclude that, in the frequency range 100--200 GHz, the contaminating effect of extragalactic sources is well below the expected anisotropy level of the cosmic mi

Daniel Schaerer, Grazyna Stasinska

Extensive grids of photoionization models have been calculated for single star HII regions and evolving starbursts. We illustrate the predictions for IR fine structure lines which are used to analyse the stellar content, and derive properties such as the age and IMF. The impact of recent ionizing fluxes on the IR lines are shown. First comparisons of our sta

Yuhri Ishimaru, Shinya Wanajo

We investigate the enrichment of europium, as a representative of r-process elements, in the Galactic halo. In present chemical evolution models, stars are assumed to be formed through shock processes by supernovae (SNe). The enrichment of the interstellar medium is calculated by a one-zone approach. The observed large dispersions in [Eu/Fe] for halo stars,

Chris Simpson, Martin Ward, Paul O'Brien, James Reeves

We present infrared photometry and optical and infrared spectroscopy of the recently-discovered, extremely luminous nearby quasar PDS 456. A number of broad emission features are seen in the near-infrared which we are unable to identify. We measure a more accurate redshift from a narrow forbidden emission line and compare the optical-infrared spectrum to tha

R. J. Protheroe

In this chapter I give an overview of shock acceleration, including a discussion of the maximum energies possible and the shape of the spectrum near cut-off, interactions of high energy cosmic rays with, and propagation through, the background radiation, and the resulting electron-photon cascade. Possible sources of the highest energy cosmic rays are discuss

Yu. A. Shchekinov

Possible observational consequences of dark matter in the Galaxy in the form of dense molecular gas clouds - clumpuscules of masses $M_c\sim 10^{-3} \msun$ and radii $R_c\sim 3\times 10^{13}$ cm - are considered. Recent models of the extreme scattering events - refraction of radio-waves from quasars in dense plasma clumps in the Galactic halo - definitely sh

W. Unruh

This paper presents an exact solution to the long wavelength perturbations for the scalar modes and for a scalar field theory with arbitrary potential. Locally these modes are coordinate transformations of the homogeneous background solutions (although non-locally they are not). These solutions are then used to discuss a couple of recent papers in which such

Mark Madsen, Carl Lipo, Michael Cannon

Dunnell's (1989) explanation for cultural elaboration proposed that elaboration could be a consequence of selection within uncertain environments. He developed the theory to the extent that it performed well explaining the distribution of elaboration at regional scales within eastern North America. More detailed studies require more detailed development

J. M. Borwein, D. M. Bradley, D. J. Broadhurst, P. Lisonek

Multiple zeta values (MZVs, also called Euler sums or multiple harmonic series) are nested generalizations of the classical Riemann zeta function evaluated at integer values. The fact that an integral representation of MZVs obeys a shuffle product rule allows the possibility of a combinatorial approach to them. Using this approach we prove a longstanding con

I. Hinchliffe, F. E. Paige

Characteristic examples are presented of scenarios of particle production and decay in supersymmetry models in which the supersymmetry breaking is transmitted to the observable world via gauge interactions. The cases are chosen to illustrate the main classes of LHC phenomenology that can arise in these models. A new technique is illustrated that allows the f

M. Boettcher, C. D. Dermer

We use a new method of analysis to determine parameters of cosmological gamma-ray bursts (GRBs), assuming that their distribution follows the star-formation history of the universe. Spectral evolution is calculated from an external shock model for fireball/blast wave evolution, and used to evaluate the measured peak flux, duration, and $νF_ν$ peak photon ene

E. Lopez

We obtain N=1 SU(N)^k gauge theories with bifundamental matter and a quartic superpotential as the low energy theory on D3-branes at singular points. These theories generalize that on D3-branes at a conifold point, studied recently by Klebanov and Witten. For k=3 the defining equation of the singular point is that of an isolated D_4 singularity. For k>3 we o

F. Lesage, H. Saleur

We explain in this paper how a meaningful irrelevant perturbation theory around the infra-red (strong coupling) fixed point can be carried out for integrable quantum impurity problems. This is illustrated in details for the spin 1/2 Kondo model, where our approach gives rise to the complete low temperature expansion of the resistivity, beyond the well known

Ori J. Ganor

We study 2+1D toroidal compactifications of M-theory with twists in the U-duality group. These compactifications realize many symmetric-manifolds from the classification of 2+1D extended supergravity moduli-spaces. We then focus on the moduli-space $SU(2,1)/U(2)$ obtained by dimensional reduction of pure N=2 supergravity in 3+1D. This space is realized with

Hiroto So, Naoya Ukita

The Ginsparg-Wilson(G-W) relation is extended for supersymmetric free theories on a lattice. Exact lattice supersymmetry(SUSY) can be defined without any ambiguities in difference operators. The lattice action constructed by a block-spin transformation is invariant under the symmetry. $U(1)_R$ symmetry on the lattice is also realized as one of exact symmetri

M. C. Bonsager, A. H. MacDonald

We report on an exploration of the mean-field phase diagram for Pauli-limited superconductivity in small metallic grains. Emphasis is placed on the crossover from the ultra-small grain limit where superconductivity disappears to the bulk thin-film limit as the single-particle level spacing in the grain decreases. We find that the maximum Zeeman coupling stre

Daniel H. T. Franco

Considering the simple chiral fermion meson model when the chiral symmetry is explicitly broken, we show the validity of a trace identity -- to all orders of perturbation theory -- playing the role of a Callan-Symanzik equation and which allows us to identify directly the breaking of dilatations with the trace of the energy-momentum tensor. More precisely, b

Seungwon Baek, Pyungwon Ko

In the minimal supersymmetric standard model (MSSM), the μ-parameter and the trilinear coupling A_t may be generically complex and can affect various observables at B factories. Imposing the edm constraints, we find that there is no new large phase shift in the B^0 - \bar{B^0} mixing, CP violating dilepton asymmetry is smaller than 0.1 %, and the direct CP v

S. Arnone, C. Fusi, K. Yoshida

Wilson's approach to renormalization group is reanalyzed for supersymmetric Yang-Mills theory. Usual demonstration of exact renormalization group equation must be modified due to the presence of the so called Konishi anomaly under the rescaling of superfields. We carry out the explicit computation for N=1 SUSY Yang-Mills theory with the simpler, gauge in

Barak Kol

Evidence is given that some particles with large charges in gauge theories, including 4d N=4 SU(3) and 5d theories with N=1 supersymmetry, have macroscopic entropy. The ground state entropy is found to be extensive in the charges. The mass gap for excitation is estimated and is of the same order as the binding energy. The question of the decay of excited sta

A. N. Aliev, M. Hortacsu, J. Kalayci, Y. Nutku

Physical properties of gravitational instantons which are derivable from minimal surfaces in 3-dimensional Euclidean space are examined using the Newman-Penrose formalism for Euclidean signature. The gravitational instanton that corresponds to the helicoid minimal surface is investigated in detail. This is a metric of Bianchi Type $VII_0$, or E(2) which admi

R. Horvat

We study the effect of adiabatically resonant conversion in galactic halos of neutrinos at the highest energies ($ \sim 10^{20}$ - $10^{22}$ eV), when the $ν$ source is in the center of a galaxy. Using the standard neutrino properties and the standard cosmological scenario for the hot dark part of matter, we find that interesting conversions may take place j

L. Ya. Glozman, D. O. Riska

Pion loop fluctuations of the constituent u and d quarks are shown to give only a minute contribution to the intrinsic charge radius of the neutron, under the assumption that the pion-quark coupling constant has its conventional value, with a cut-off scale of the order of 1.0 GeV. The contribution from the pion loops to the anomalous magnetic moment of the n

P. Picchi, F. Pietropaolo

We present an overview of the future projects concerning the neutrino oscillation physics in Europe. Recently a joint CERN-LNGS scientific committee has reviewed several proposals both for the study of atmospheric neutrinos and for long (LBL) and short baseline (SBL) neutrino oscillation experiments. The committee has indicated the priority that the European

Hiroyuki Yamase, Hiroshi Kohno, Hidetoshi Fukuyama, Masao Ogata

In the vicinity of hole density, 1/8, La-based high-$T_{c}$ superconductors exhibit long-range order of incommensurate antiferromagnetism (IC-AF). Motivated by this observation, we explore the possible stabilization of IC-AF ordering due to the existence of static charge density modulation (CDM). We use Ginzburg-Landau free energy based on the mean field the

Sushan Konar, Dipankar Bhattacharya

The evolutionary scenario of the neutron star magnetic field is examined assuming a spindown-induced expulsion of magnetic flux originally confined to the core, in which case the expelled flux undergoes ohmic decay. The nature of field evolution, for accreting neutron stars, is investigated incorporating the crustal microphysics and material movement due to

Hiroshi Suzuki

The chiral Jacobian, which is defined with Neuberger's overlap Dirac operator of the lattice fermion, is explicitly evaluated in the continuum limit without expanding it in the gauge coupling constant. Our calculational scheme is simple and straightforward. We determine a coefficient of the chiral anomaly for general values of the mass parameter and the

Philippe Pouliot

The Molien function counts the number of independent group invariants of a representation. For chiral superfields, it is invariant under duality by construction. We illustrate how it calculates the spectrum of supersymmetric gauge theories.

A. I. Fedoseyev, M. J. Friedman, E. J. Kansa

The Multiquadric Radial Basis Function (MQ) Method is a meshless collocation method with global basis functions. It is known to have exponentional convergence for interpolation problems. We descretize nonlinear elliptic PDEs by the MQ method. This results in modest size systems of nonlinear algebraic equations which can be efficiently continued by standard c

Takeshi Sato

We derive superalgebras in many types of supersymmetric M-brane backgrounds. The backgrounds examined here include the cases of the M-wave and the M-Kaluza-Klein monopole. On the basis of the obtained algebras, we deduce all the supersymmetric non-orthogonal intersections of the M-Kaluza-Klein monopole and the M-5-brane at angles. In addition, we present a 1

Fuqiang Wang

Single-particle spectra and two-particle correlation functions measured by the NA49 collaboration in central Pb+Pb collisions at 158 GeV/nucleon are presented. These measurements are used to study the kinetic and chemical freeze-out conditions in heavy ion collisions. We conclude that large baryon stopping, high baryon density and strong transverse radial fl

G. K. Fanourakis, D. Fassouliotis, A. Leisos, N. Mastroyiannopoulos

This paper describes the extension of the Modified Observables technique in estimating simultaneously more than one Trilinear Gauge Couplings. The optimal properties, unbiasedness and consistent error estimation of this method are demonstrated by Monte Carlo experimentation using $\ell \nu jj $ four-fermion final state topologies. Emphasis is given in the de

C. S. Reynolds, S. Heinz, A. C. Fabian, M. C. Begelman

We present hard X-ray observations of the nearby radio galaxy M87 and the core of the Virgo cluster using the Rossi X-ray Timing Explorer. These are the first hard X-ray observations of M87 not affected by contamination from the nearby Seyfert 2 galaxy NGC4388. Thermal emission from Virgo's intracluster medium is clearly detected and has a spectrum indic

Antoine Suarez

It is argued that the three assumptions of quantum collapse, one photon-one count, and relativity of simultaneity cannot hold together: Nonlocal correlations can depend on the referential frames of the beam-splitters but not of the detectors. New experiments using interferometers in series are proposed which make it possible to test Quantum Mechanics vs Mult

V M Red'kov

In the literature concerning the monopole matter, three gauges: Dirac, Schwinger, and Wu-Yang's, have been contrasted to each other, and the Wu-Yang's often appears as the most preferable one. The article aims to analyse this view by interpreting the monopole situation in terms of the conventioal Fourier series theory; in particular, having relied on

V M Red'kov

It is shown that the manner of introducing theinteraction between a spin 1 particle and external classical gravitational field can be successfully uni- fied with the approach that occurred with regard to a spin 1/2 particle and was first developed by Tetrode, Weyl, Fock, Ivanenko. On that way a general- ly relativistical Duffin-Kemmer equation is costructed.

K. Horie, H. Miyazaki, I. Tsutsui, S. Tanimura

We study classical and quantum caustics for system with quadratic Lagrangian. Gaussian slit experiment is examined and it is pointed out that the focusing around caustics is stabilized against initial momentum fluctuations by quantum effect.

A. A. Zhmudsky

An analytical-numeric calculation method of extremely complicated integrals is presented. These integrals appear often in magnet soliton theory. The appropriate analytical continuation and a corresponding integration contour allow to reduce the calculation of wide class of integrals to a numeric search of integrand denominator roots (in a complex plane) and

V. V. Maximov N. E. Molevich, I. P. Zavershinsky, A. P. Zubarev

We found the energetic stability criteria of non-equilibrium gase plain flows.

Gary Prezeau

This paper describes the derivation of a new representation of an $SU(2)_L \times SU(2)_R$ locally-invariant model of the strong interactions called quantum hadrodynamics 3 (QHD-III). QHD-III is a gauge-invariant theory based on the linear $σ$ model, the gauge bosons being the $ρ$ and the $a_1$. The new representation considerably simplifies the lagrangian.

E. Gedalin, A. Moalem, L. Razdolskaya

We consider tree diagram contributions to neutral pion production in pp ->pp pi0 using chiral perturbation theory in the relativistic and extremely non-relativistic limits. In marked difference with the results from heavy fermion formalism, the impulse and s-wave rescattering terms in the relativistic limit have equal signs and therefore add constructively,

A. F. R. de Toledo Piza, M. S. Hussein, B. V. Carlson, C. A. Bertulani

Isospin is included in the description of Coulomb excitation of multiple giant isovector dipole resonances. In the excitation of even-even nuclei, a relevant portion of the excitation strength is shown to be associated with 1+ two-phonon states, which tends to be hindered or completely supressed in calculations in which the isospin degree of freedom is not c

E. Gedalin, A. Moalem, L. Razdolskaja

The production rate for η' in pp ->pp η' at rest is calculated in a covariant one boson exchange model, previously applied to study pi^0 and ηproduction in NN collisions. The transition amplitudes for the elementary BN -> eta' N processes with B being the meson exchanged (B = pi, sigma, eta, rho, omega and delta) are taken to be the sum of s and

Sourav Sarkar, Pradip Roy, Jan-e Alam, Bikash Sinha

The effects of the variation of vector meson masses and decay widths on photon production from hot strongly interacting matter formed after Pb + Pb and S + Au collisions at CERN SPS energies are considered. It has been shown that the present photon spectra measured by WA80 and WA98 Collaborations can not distinguish between the formation of quark matter and

Boris Krippa

The constraints imposed by chiral symmetry on hadron correlation functions in nuclear medium are discussed. It is shown that these constraints implies the certain structure of the in-medium hadron correlators and lead to the cancellation of the order $ρm_π$ term in the in-medium nucleon correlator. We also consider the effect of mixing of the chiral partners

S. Meljanac, M. Milekovic, M. Stojic

We study exclusion statistics within the second quantized approach. We consider operator algebras with positive definite Fock space and restrict them in a such a way that certain state vectors in Fock space are forbidden ab initio.We describe three characteristic examples of such exclusion, namely exclusion on the base space which is characterized by states

Ravi Vakil

The characteristic numbers of smooth plane quartics are computed using intersection theory on a component of the moduli space of stable maps. This completes the verification of Zeuthen's prediction of characteristic numbers of smooth plane curves. A short sketch of a computation of the characteristic numbers of plane cubics is also given as an illustrati

R. M. Kashaev, A. Yu. Volkov

Modified universal R-matrices, associated with the central extension (through the Drinfeld's double construction) of the quantum groups U_q(sl_n), are realized through an infinite dimensional spectral parameter dependent solution for the tetrahedron equation, provided a certain identity on $q$-exponentials holds true.

Susan Tolman, Jonathan Weitsman

Let $M$ be a symplectic manifold, equipped with a semifree symplectic circle action with a finite, nonempty fixed point set. We show that the circle action must be Hamiltonian, and $M$ must have the equivariant cohomology and Chern classes of $(P^1)^n$.

Zu-Guo Yu

In this paper we introduce some families of fuzzy L-systems and investigate their properties. We further discuss the relationship between fuzzy L languages and the fuzzy languages generated by fuzzy grammar proposed in Ref.[3,5]. A measure of fuzziness for a string, called the fuzzy entropy of a string with respect to a given fuzzy L system, will be defined.

Susan Tolman, Jonathan Weitsman

Let $M$ be a symplectic manifold equipped with a Hamiltonian action of a torus $T$. Let $F$ denote the fixed point set of the $T$-action and let $i:F\hookrightarrow M$ denote the inclusion. By a theorem of F. Kirwan \cite{K} the induced map $i^*:H_T^*(M) \to H_T^*(F)$ in equivariant cohomology is an injection. We give a simple proof of a formula of Goresky-K

D. Kutasov, F. Larsen, R. Leigh

We discuss string propagation in the near-horizon geometry generated by Neveu-Schwarz fivebranes, Kaluza-Klein monopoles and fundamental strings. When the fivebranes and KK monopoles are wrapped around a compact four-manifold $\MM$, the geometry is $AdS_3\times S^3/\ZZ_N\times \MM$ and the spacetime dynamics is expected to correspond to a local two dimension

G. Akemann, R. Grimm, M. Hasler, C. Herrmann

We extend the notion of central charge superspace to the case of local supersymmetry. Gauged central charge transformations are identified as diffeomorphisms at the same footing as space-time diffeomorphisms and local supersymmetry transformations. Given the general structure we then proceed to the description of a particular vector-tensor supergravity multi

F. J. de Urries, J. Julve

As an alternative to the covariant Ostrogradski method, we show that higher-derivative relativistic Lagrangian field theories can be reduced to second differential-order by writing them directly as covariant two-derivative theories involving Lagrange multipliers and new fields. Notwithstanding the intrinsic non-covariance of the Dirac's procedure used to

T. Padmanabhan

Points of conflict between the principles of general relativity and quantum theory are highlighted. I argue that the current language of QFT is inadequete to deal with gravity and review attempts to identify some of the features which are likely to present in the correct theory of quantum gravity.

Shin'ichi Nojiri, Sergei D. Odintsov

We discuss dilatonic gravity (bulk theory) from the point of view of (generalized) AdS/CFT correspondence. Self-consistent dilatonic background is considered. It may be understood as two boundaries space where AdS boundary appears as infinite boundary and new (singular) boundary occurs at short distances. The two-point correlation function and conformal dime

Christopher Kolda, David H. Lyth

Models of supersymmetric D-term inflation require a new mass scale near 10^{15-16} GeV in order to match the density perturbation spectrum observed by COBE. Attempts to obtain such a scale from the anomalous U(1) of string theories fail in most string models. However there is hope that models based on non-standard embeddings in M-theory can solve the discrep

Laura Covi

We realize and study a model of hybrid inflation in the context of softly broken supersymmetry. The inflaton is taken to be a flat direction in the superfield space and, due to unsuppressed couplings, its soft supersymmetry breaking mass runs with scale. Both gauge and Yukawa couplings are taken into account and different inflationary scenarios are investiga

A. De Rujula, W. Vogelsang

We argue that existing measurements of ep collisions at HERA --in which an energetic photon is made via a QED `Compton' subprocess-- can provide rather detailed information on the photonic parton density of the proton. This function and its deviations from Bjorken scaling should be measurable, allowing for an interesting test of the theory. The photonic

Werner Porod

We discuss the three-body decays stop_1 -> W^+ b neutralino_1, stop_1 -> H^+ b neutralino_1, stop_1 -> b slepton_i neutrino_l, and stop_1 -> b sneutrino_l l^+$ ($l =e,μ,τ$) of the lighter top squark within the minimal supersymmetric standard model. We give the complete analytical formulas for the decay widths and present a numerical study in view of an upgra

Marcelo Hott, Georgios Metikas

We examine a very simple model for which the leading contribution to the one-loop effective potential at finite temperature is uniquely defined despite the presence of the Landau terms. In addition we report on the usual non-analyticity at finite temperature in order to compare our perturbative results with exact ones obtained in the literature. Finally, we

M. Konchtnij, N. P. Merenkov

The electron current tensor for the scattering of heavy photon on longitudinally polarized electron accompanied with two hard real photonsis considered. The contribution of collinear and semicollinear kinematics is computed. The obtained result allows to calculate the corresponding contribution into second order radiative correction to DIS or electron-positr

A. Masiero, T. Yanagida

We propose a new mechanism called "real CP violation" to originate spontaneous CP violation. Starting with a CP conserving theory with scalar fields in the adjoint representation of a global or local non-abelian symmetry, we show that even though the VEV's of such scalars are real they give rise to a spontaneous violation of CP. We provide an ill

Tatsuo Kobayashi, Jisuke Kubo, Myriam Mondragon, George Zoupanos

The evolution of the parameters including those in the soft supersymmetry-breaking (SSB) sector is studied in the minimal supersymmetric standard model (MSSM) with a certain set of Kaluza-Klein towers which has been recently considered by Dienes et al. We use the continuous Wilson renormalizaion group technique to derive the matching condition between the ef

Da-Shin Lee, Kin-Wang Ng

We study the nonequilibrium photon production in the quark-hadron phase transition, using the Friedberg-Lee type solitons as a working model for quark-hadron physics. We propose that to search for nonequilibrium photons in the direct photon measurements of heavy-ion collisions may be a characteristic test of the transition from the quark-gluon to hadronic ph

Dal Soo Oh, M. H. Reno

We evaluate the sensitivity of the Large Hadron Collider (LHC) to charged heavy vector boson production followed by their decays to $W^\pm Z^0$. We include the correlated decays of the gauge bosons to leptonic final states. With an integrated luminosity of $10^5$ pb$^{-1}$, charged technirhos in the minimal SU(N)$_{TC}$ model for $N\geq 7$ yield signals with

A. P. Martynenko, V. A. Saleev

We consider the production of ultrarelativistic parapositronium and orthopositronium atoms in collisions of high energy electrons with laser photons. Our results demonstrate the opportunity of intensive positronium beam formation with Lorentz-factor 10^6 using laser beam conversion on high energy electrons at the future Electron Linear Accelerators.

C. S. Lim

Lepton-flavour violating processes, such as $μ\to eγ$, are studied in ordinary (non-SUSY) SU(5) and SUSY SU(5) grand unified theories. First given are some introductory argument on the mechanism of U.V. divergence cancellation in flavour changing neutral current processes and on the decoupling of particles with GUT scale masses . We next see that such genera

Jorge C. Romao

In these Lectures we review the Minimal Supersymmetric Standard Model as well as some of its extensions that include R-Parity violation. The cases of spontaneous breaking of R-Parity as well as that of explicit violation through bilinear terms in the superpotential are studied in detail. The signals at LEP and the prospects for LHC are discussed.

J. C. Thompson

New studies of hadronic event shape observables in e+ e- collisions between 13 and 183 GeV CM energy have enabled the running of alpha_s to be confirmed and the validity of non-perturbative power-law corrections to be investigated. A more precise value of alpha_s(M_Z) with reduced theoretical errors has been reported from fitting 18 oriented event shape dist

R. Barate

This contribution concerns three contributed papers that share the common feature of analysing fully- (or almost fully-) reconstructed B decays coming from a sample of four million hadronic Z decays collected with the ALEPH detector at LEP...

J. Wainwright, M. J. Hancock, C. Uggla

We study the late time evolution of a class of exact anisotropic cosmological solutions of Einstein's equations, namely spatially homogeneous cosmologies of Bianchi type VII$_0$ with a perfect fluid source. We show that, in contrast to models of Bianchi type VII$_h$ which are asymptotically self-similar at late times, Bianchi VII$_0$ models undergo a com

N. Pauna, I. V. Vancea

It has been recently shown that in order to have Dirac eigenvalues as observables of Euclidean supergravity, certain constraints should be imposed on the covariant phase space as well as on Dirac eigenspinors. We investigate the relationships among the constraints in the first set and argue that these relationships are not linear. We also derive a set of equ

David Polarski

We show how the quantum-to-classical transition of the cosmological fluctuations produced during an inflationary stage can be described using the consistent histories approach. We identify the corresponding histories in the limit of infinite squeezing. To take the decaying mode into account, we propose an extension to coarse-grained histories.

Angelo M. Anile, Diego Pavon, Vittorio Romano

In this paper we highlight the fact that the physical content of hyperbolic theories of relativistic dissipative fluids is, in general, much broader than that of the parabolic ones. This is substantiated by presenting an ample range of dissipative fluids whose behavior noticeably departs from Navier-Stokes'.

H. F. Fong, P. Bourges, Y. Sidis, L. P. Regnault

The magnetic excitation spectrum of a YBa_2 Cu_3 O_7 crystal containing 0.5% of nonmagnetic (Zn) impurities has been determined by inelastic neutron scattering. Whereas in the pure system a sharp resonance peak at E ~ 40 meV is observed exclusively below the superconducting transition temperature T_c, the magnetic response in the Zn-substituted system is bro

Paul Pichaureau, Rodolfo A. Jalabert

We derive a semiclassical scheme for the conductance through a rectangular cavity. The transmission amplitudes are expressed as a sum over families of trajectories rather than a sum over isolated trajectories. The contributing families are obtained from the evaluation of a finite number of continued fractions. We find that, contrary to the chaotic case, the

Uwe Micka, Christian Holm, Kurt Kremer

We present a set of molecular dynamics (MD) simulations of strongly charged, flexible polyelectrolyte chains under poor solvent conditions in a salt free solution. Structural properties of the chains and of the solutions are reported. By varying the polymer density and the electrostatic interaction strength we study the crossover from a dominating electrosta

A. Cuccoli, V. Tognetti, R. Giachetti, R. Maciocco

The pure-quantum self-consistent harmonic approximation (PQSCHA) permits to study a quantum system by means of an effective classical Hamiltonian. In this work the PQSCHA is reformulated in terms of the holomorphic variables connected to a set of bosonic operators. The holomorphic formulation, based on the olomorphic path integral for the Weyl symbol of the

A. Cuccoli, V. Tognetti, P. Verrucchi, R. Vaia

The pure-quantum self-consistent harmonic approximation, a semiclassical method based on the path-integral formulation of quantum statistical mechanics, is applied to the study of the thermodynamic behaviour of the quantum Heisenberg antiferromagnet on the square lattice (QHAF). Results for various properties are obtained for different values of the spin and

V. Zhuravlev, T. Maniv, I. D. Vagner, P. Wyder

Phase fluctuations in the superconducting order parameter, which are responsible for the melting of the Abrikosov vortex lattice below the mean field $H_{c2}$, are shown to dramatically enhance the scattering of quasi-particles by the fluctuating pair potential, thus leading to enhanced damping of the dHvA oscillations in the liquid mixed state. This effect

M. A. Moore, A. Perez-Garrido

Vortices in thin-film superconductors are often modelled as a system of particles interacting via a repulsive logarithmic potential. Arguments are presented to show that the hypothetical (Abrikosov) crystalline state for such particles is unstable at any finite temperature against proliferation of screened disclinations. The correlation length of crystalline

Dario Alfe`, Stefano de Gironcoli, Stefano Baroni

Nickel and Rhodium (001) surfaces display a similar - as from STM images - clock reconstruction when half a monolayer of C/Ni, N/Ni or O/Rh is adsorbed; no reconstruction is observed instead for O/Ni. Adsorbate atoms sit at the center of the black squares of a chess-board, $c(2\times 2)$, pattern and two different reconstructions are actually compatible with

Ryo Tamura, Masaru Tsukada

The band structures of the periodic nanotube junctions are investigated by the effective mass theory and the tight binding model. The periodic junctions are constructed by introducing pairs of a pentagonal defect and a heptagonal defect periodically in the carbon nanotube. We treat the periodic junctions whose unit cell is composed by two kinds of metallic n

Clara Saluena, Thorsten Poeschel, Sergei E. Esipov

We investigate collective dissipative properties of vibrated granular materials by means of molecular dynamics simulations. Rates of energy losses indicate three different regimes or "phases"in the amplitude-frequency plane of the external forcing, namely, solid, convective, and gas-like regimes. The behavior of effective damping decrement in the sol

R. T. F. van Schaijk, A. de Visser, S. Olsthoorn, H. P. Wei

We report quantum Hall experiments on the plateau-insulator transition in a low mobility In_{.53} Ga_{.47} As/InP heterostructure. The data for the longitudinal resistance ρ_{xx} follow an exponential law and we extract a critical exponent κ= .55 \pm .05 which is slightly different from the established value κ= .42 \pm .04 for the plateau transitions. Upon c

T. Temesvari, C. De Dominicis, I. Kondor

Replica field theory for the Ising spin glass in zero magnetic field is studied around the upper critical dimension d=6. A scaling theory of the spin glass phase, based on Parisi's ultrametrically organised order parameter, is proposed. We argue that this infinite step replica symmetry broken (RSB) phase is nonperturbative in the sense that amplitudes of

P. Fulde, H. Stoll, K. Kladko

We formulate the calculation of the ground-state wavefunction and energy of a system of strongly correlated electrons in terms of scattering matrices. A hierarchy of approximations is introduced which results in an incremental expansion of the energy. The present approach generalizes previous work designed for weakly correlated electronic systems.

X. Hu, T. Koyama, M. Tachiki

Temperature vs. chemical-potential phase diagrams of an SO(5) model for high-(T_c) cuprates are calculated by Monte Carlo simulation. There is a bicritical point where the second-order antiferromagnetism (AF) and superconductivity transition lines merge tangentially into a first-order line, and the SO(5) symmetry is achieved. In an external magnetic field, t

C. Reichhardt, F. Nori

Using numerical simulations, we observe phase locking, Arnold tongues, and Devil's staircases for vortex lattices driven at varying angles with respect to an underlying superconducting periodic pinning array. This rich structure should be observalble in transport measurments. The transverse $V(I)$ curves have a Devil's staircase structure, with plate

S. M. Alamoudi, D. Boyanovsky, H. J. de Vega

We study the dynamics of relaxation and thermalization in an exactly solvable model of a particle interacting with a harmonic oscillator bath. Our goal is to understand the effects of non-Markovian processes on the relaxational dynamics and to compare the exact evolution of the distribution function with approximate Markovian and Non-Markovian quantum kineti

Sumio Ishihara, Sadamichi Maekawa

We study theoretically the collective orbital excitation named orbital wave in the orbital ordered manganites.The dispersion relation of the orbital wave is affected by the static spin structure through the coupling between spin and orbital degrees of freedom. As a probe to detect the dispersion relation, we propose two possible methods by utilizing resonant

Y. Lin, J. Sichelschmidt, J. E. Eldridge, T. Wahlbrink

We reported two-magnon Raman scattering from La_{1.9}Sr_{0.1}CuO_4, which has a suppressed Tc=12 K, as the temperature is lowered below 37 K and an ordered spin phase is formed. The two-magnon Raman intensity increases with decreasing temperature. The magnetic scattering in La_{1.9}Sr_{0.1}CuO_4 is totally different from that reported in the parent compound

Kazuhiko Kuroki, Hideo Aoki

The d-wave pairing correlations along with spin correlation are calculated with quantum Monte Carlo method for the two-dimensional Hubbard model on lattice structures representing organic superconductors $κ$-(BEDT-TTF)$_2$X and (TMTSF)$_2$X. In both cases the pairing correlations for superconducting order parameters with nodes are found to be enhanced. The s

R. R. Du, D. C. Tsui, H. L. Stormer, L. N. Pfeiffer

Low-temperature, electronic transport in Landau levels N>1 of a two-dimensional electron system is strongly anisotropic. At half-filling of either spin level of each such Landau level the magnetoresistance either collapses to form a deep minimum or is peaked in a sharp maximum, depending on the in-plane current direction. Such anisotropies are absent in the

Marc Mezard

The recently proposed strategy for studying the equilibrium thermodynamics of the glass phase using a molecular liquid is reviewed and tested in details on the solvable case of the $p$-spin model. We derive the general phase diagram, and confirm the validity of this procedure. We point out the efficacy of a system of two weakly coupled copies in order to ide

A. F. Volkov

Comment withdrawn. To be superseded by a subseqent paper.

C. De Dominicis, T. Temesvari, I. Kondor

The introduction of ``small permutations'' allows us to derive Ward-Takahashi identities for the spin-glass, in the Parisi limit of an infinite number of steps of replica symmetry breaking. The first identities express the emergence of a band of Goldstone modes. The next identities relate components of (the Replica Fourier Transformed) 3-point functi

P. D. Ditlevsen

The 2d and 3d like Gletzer, Okhitani and Yamada (GOY) shell models are examined. The 2d like model shows a transition from statistical quasi-equilibrium to cascade of enstrophy as a function of the spectral ratio of energy to enstrophy. The transition is related to the ratio of time scales, corresponding to eddy turnover times, between shells. The anomalous