June 1999 arXiv papers — page 12

Florian Jasch, Hagen Kleinert

We develop an efficient algorithm for evaluating divergent perturbation expansions of field theories in the bare coupling constant g_B for which we possess a finite number L of expansion coefficients plus two more informations: The knowledge of the large-order behavior proportional to (- alpha)^kk!k^beta g_B^k, with a known growth parameter alpha, and the kn

Nivaldo A. Lemos, Flavio G. Alvarenga

First a Friedmann-Robertson-Walker (FRW) universe filled with dust and a conformally invariant scalar field is quantized. For the closed model we find a discrete set of wormhole quantum states. In the case of flat spacelike sections we find states with classical behaviour at small values of the scale factor and quantum behaviour for large values of the scale

U. Bassler, E. Laenen, A. Quadt, H. Schellman

We summarize the experimental and theoretical results presented in the ``Structure Function Working Group - WG1'' at DIS'99.

Yuri B. Suris

We include the relativistic lattice KP hierarchy, introduced by Gibbons and Kupershmidt, into the $r$-matrix framework. An $r$-matrix account of the nonrelativistic lattice KP hierarchy is also provided for the reader's convenience. All relativistic constructions are regular one-parameter perturbations of the nonrelativistic ones. We derive in a simple w

B. Alles, M. Pepe

We calculate up to four loops the free energy of the two-dimensional (2D) O(n) nonlinear sigma-model regularized on the lattice with the 0-loop and 1-loop Symanzik improved actions. An effective coupling constant based on this calculation is defined.

A. B. Lahanas, D. V. Nanopoulos, V. C. Spanos

We discuss the relic density of the lightest of the supersymmetric particles ({\small LSP}) in view of new cosmological data, which favour the concept of an accelerating Universe with a non-vanishing cosmological constant. The new bound on the Cold Dark Matter density, $Ω_{\mathrm{CDM}} h_0^2 \lesssim 0.22$, puts stringent constraints on supersymmetry prefer

Kazuhiro Kuboki

We study the proximity effects near the interface between a d-wave superconductor (S) and a ferromagnet (F) or an antiferromagnet (AF). The S-side (F and AF-side) is described by the attractive (repulsive) Hubbard model, and the Bogoliubov de Gennes equation derived within the Hartree-Fock approximation is solved numerically. The superconducting order parame

Jens Fjelstad, Stephen Hwang

The equivalence between the Chern-Simons gauge theory on a three-dimensional manifold with boundary and the WZNW model on the boundary is established in a simple and general way using the BRST symmetry. Our approach is based on restoring gauge invariance of the Chern-Simons theory in the presence of a boundary. This gives a correspondence to the WZNW model t

I. Brevik

The recent theory of 't Hooft [ Nucl. Phys. Suppl. {\bf 68}, 174 (1998)] models the black hole as a system endowed with an envelope of matter that obeys an equation of state in the form $ p=(γ-1)ρ$, and acts as a source in Einstein's equations. The present paper generalizes the 't Hooft theory so as to take into account a bulk viscosity $ζ$ in th

B. J. Nauta

Real-time classical SU($N$) gauge theories at non-zero temperature contain linear divergences. We introduce counterterms for these divergences in the equations of motion in the continuum and on the lattice. These counterterms can be given in terms of auxiliary fields that satisfy local equations of motion. We present a lattice model with 6+1D auxiliary field

M. Henneaux, A. Wilch

We determine all the terms that are gauge-invariant up to a total spacetime derivative ("semi-invariant terms") for gauged non-linear sigma models. Assuming that the isotropy subgroup $H$ of the gauge group is compact or semi-simple, we show that (non-trivial) such terms exist only in odd dimensions and are equivalent to the familiar Chern-Simons ter

A. Montero

We present a new way of fixing the gauge to (direct) maximal center gauge in SU(N) Yang-Mills theory and apply this method to SU(3) configurations which are vortex-like. We study the structure of the Z_3 configurations obtained after center-projecting the SU(3) ones.

Yutaka Okamoto, Masaki Yasue

In SU(3)_L x U(1)_N gauge models for electroweak interactions, we discuss how to implement a radiative mechanism of generating Majorana neutrino masses by considering the property that the Higgs scalar, which has a coupling to a charged lepton (\ell)-neutrino (ν) pair, is naturally included. The mechanism is shown to work in models with a heavy charged lepto

P. G. Dommersnes, J. -B. Fournier

We study the collective behavior of inclusions inducing local anisotropic curvatures in a flexible fluid membrane. The N-body interaction energy for general anisotropic inclusions is calculated explicitly, including multi-body interactions. Long-range attractive interactions between inclusions are found to be sufficiently strong to induce aggregation. Monte

M. Czakon, J. Gluza, M. Zralek

Two general models with hierarchical and almost degenerate neutrino masses, which are able to explain the solar and atmospheric anomalies are investigated. We show how neutrinoless double beta decay experiments discern Dirac and Majorana natures of neutrinos. The strongest result is, that almost degenerate neutrinos with masses above 0.22 eV combined with th

T. Fujita, T. Kake, H. Takahashi

We study the strong coupling limit of the Bethe ansatz solutions in the massive Thirring model. We find analytical expressions for the energy eigenvalues for the vacuum state as well as n-particle n- hole states. This formula is compared with the numerical results and is found to achieve a very good agreement. Also, it is found that the 2-particle 2- hole an

T. Sensui, Y. Funato, J. Makino

We investigated the evolution of clusters of galaxies using self-consistent $N$-body simulations in which each galaxy was modeled by many particles. We carried out simulations for about 20 cases using different initial conditions. In all simulations, clusters were initially in virial equilibrium. We found that more than half of the total mass escaped from in

Hiroyuki Satoh, Fusayoshi J. Ohkawa

Based on the periodic Anderson model, it is shown that the competition between the quenching of magnetic moments by local quantum spin fluctuations and a magnetic exchange interaction caused by the virtual exchange of pair excitations of quasiparticles in spin channels is responsible for the metamagnetic crossover in CeRu_2Si_2, cooperated with the electron-

Masakatsu Kenmoku, Hiroto Kubotani, Eiichi Takasugi, Yuki Yamazaki

We discuss the implications of a wave function for quantum gravity, which involves nothing but 3-dimensional geometries as arguments and is invariant under general coordinate transformations. We derive an analytic wave function from the Wheeler-DeWitt equation for spherically symmetric space-time with the coordinate system arbitrary. The de Broglie-Bohm inte

V. Avila-Reese, C. Firmani, A. Klypin, A. V. Kravtsov

(Abridged) We study the outer density profiles of dark matter haloes predicted by a generalized secondary infall model and observed in a N-body cosmological simulation of a ΛCDM model. We find substantial systematic variations in shapes and concentrations of the halo profiles as well as a strong correlation of the profiles with the environment. In the N-body

Dongsu Bak, Choonkyu Lee, Kimyeong Lee, Piljin Yi

Classical 1/4 BPS configurations consist of 1/2 BPS dyons which are positioned by competing static forces from electromagnetic and Higgs sectors. These forces do not follow the simple inverse square law, but can be encoded in some low energy effective potential between fundamental monopoles of distinct types. In this paper, we find this potential, by compari

Cynthia K. W. Ma

Philosophical analyses of causation take many forms but one major difficulty they all aim to address is that of the spatio-temporal continuity between causes and their effects. Bertrand Russell in 1913 brought the problem to its most transparent form and made it a case against the notion of causation in physics. In this essay, I focus on this subject of caus

P. Facchi, S. Pascazio, A. Scardicchio

We study the dynamics of a "kicked" quantum system undergoing repeated measurements of momentum. A diffusive behavior is obtained for a large class of Hamiltonians, even when the dynamics of the classical counterpart is not chaotic. These results can be interpreted in classical terms by making use of a "randomized" classical map. We compute t

Yaakov S. Weinstein, Seth Lloyd, David G. Cory

The quantum Fourier transform (QFT) has been implemented on a three bit nuclear magnetic resonance (NMR) quantum computer, providing a first step towards the realization of Shor's factoring and other quantum algorithms. Implementation of the QFT is presented with fidelity measures, and state tomography. Experimentally realizing the QFT is a clear demonst

E. Comay

Quantum mechanical foundations of the polarized neutron phase shift experiment are discussed. The fact that the neutron retains its ground state throughout the experiment is shown to be crucial for the phase shift obtained.

Carl M. Bender, Stefan Boettcher, H. F. Jones, Van M. Savage

Recently, a class of PT-invariant quantum mechanical models described by the non-Hermitian Hamiltonian $H=p^2+x^2(ix)^ε$ was studied. It was found that the energy levels for this theory are real for all $ε\geq0$. Here, the limit as $ε\to\infty$ is examined. It is shown that in this limit, the theory becomes exactly solvable. A generalization of this Hamilton

Guang-jiong Ni

Several new physics experiments in 1998 were performed and analyzed to show the subtlety of quantum theory, including the "wave-particle duality" and the non-separability of two-particle entangled state. Here it is shown that the measurement is bound to change the object by destroying the original quantum coherence between the object and its environm

E. G. Kalnins, W. Miller,, G. S. Pogosyan

In this paper we construct generalizations to spheres of the well known Levi-Civita, Kustaanheimo-Steifel and Hurwitz regularizing transformations in Euclidean spaces of dimensions 2, 3 and 5. The corresponding classical and quantum mechanical analogues of the Kepler-Coulomb problem on these spheres are discussed.

P. Oscar Boykin, Tal Mor, Matthew Pulver, Vwani Roychowdhury

A novel universal and fault-tolerant basis (set of gates) for quantum computation is described. Such a set is necessary to perform quantum computation in a realistic noisy environment. The new basis consists of two single-qubit gates (Hadamard and ${σ_z}^{1/4}$), and one double-qubit gate (Controlled-NOT). Since the set consisting of Controlled-NOT and Hadam

Zhen Wang

The deflection of light ray passing near the Sun is calculated with quantum-corrected Newton's gravitation law. The satisfactory result suggests that there may exist other theoretical possibilities besides the theory of relativity.

Michael K. -H. Kiessling

It is shown that the traditional conservation laws for total charge, energy, linear and angular momentum, hold jointly in classical electron theory if and only if classical electron spin is included as dynamical degree of freedom.

R. D. Pisarski, D. H. Rischke

We give a pedagogical discussion of how color superconductivity can produce parity violation in cold quark matter at very high densities.

James J. Kelly

We propose a new method for measuring longitudinal amplitudes for electroproduction of pseudoscalar mesons that exploits a symmetry relation for polarization observables in parallel kinematics. This polarization technique does not require variation of electron scattering kinematics and avoids the major sources of systematic errors in Rosenbluth separation.

Joel L. Lebowitz, Marco Lenci, Herbert Spohn

We consider a general d-dimensional quantum system of non-interacting particles, with suitable statistics, in a very large (formally infinite) container. We prove that, in equilibrium, the fluctuations in the density of particles in a subdomain of the container are described by a large deviation function related to the pressure of the system. That is, untypi

D. Hundertmark, A. Laptev, T. Weidl

Improved estimates on the constants $L_{γ,d}$, for $1/2<γ<3/2$, $d\in N$ in the inequalities for the eigenvalue moments of Schrödinger operators are established.

A. Laptev, T. Weidl

We show how a matrix version of the Buslaev-Faddeev-Zakharov trace formulae for a one-dimensional Schrödinger operator leads to Lieb-Thirring inequalities with sharp constants $L^{cl}_{γ,d}$ with $γ\ge 3/2$ and arbitrary $d\ge 1$. (revised, to appear in Acta Math)

J. Brian Conrey, Andrew Granville, Bjorn Poonen, K. Soundararajan

The authors study the distribution of zeros of the Fekete polynomial f_p(t) (defined for p prime) as p -> infinity. They show that asymptotically a constant fraction of the zeros lie on the unit circle, and they investigate the constant of proportionality.

Saharon Shelah

This is a non-standard paper, containing some problems in set theory I have in various degrees been interested in. Sometimes with a discussion on what I have to say; sometimes, of what makes them interesting to me, sometimes the problems are presented with a discussion of how I have tried to solve them, and sometimes with failed tries, anecdote and opinion.

G. W. Patrick

Stable assemblages of localized vortices exist which have particle-like properties, such as mass, and which can interact with one another when they closely approach. In this article I calculate the mass of these localized states and numerically investigate some aspects of their interactions.

Neil P. Strickland

Let G be a finite group, and let E be a generalised cohomology theory, subject to certain technical conditions. We study a certain ring C(E,G) that is the best possible approximation to E^0BG that can be built using only knowledge of the complex representations of G. There is a natural map C(E,G) -> E^0BG, whose image is the subring of E^0BG generated over E

Yucai Su

We classify the finite dimensional indecomposable sl(m/n)-modules with at least a typical or singly atypical primitive weight. We do this classification not only for weight modules, but also for generalized weight modules. We obtain that such a generalized weight module is simply a module obtained by ``linking&#39;&#39; sub-quotient modules of generalized Ka

Hélène Esnault, Marc Levine

We construct 0-cycles on the product of 2 elliptic curves, which are not detectable by Bloch&#39;s analytic motivic cohomology.

Tom Banks

I present cosmological arguments which point towards a Horava-Witten like picture of the universe, with the unification scale of order the fundamental gravitational scale. The SUSY breaking scale is determined by the dynamics of gauge fields which are weakly coupled at the fundamental scale. Bulk moduli whose potential originates at short distances are the i

A. Bassetto, L. Griguolo, F. Vian

The exact expression for Wilson loop averages winding n times on a closed contour is obtained in two dimensions for pure U(N) Yang-Mills theory and, rather surprisingly, it displays an interesting duality in the exchange $n \leftrightarrow N$. The large-N limit of our result is consistent with previous computations. Moreover we discuss the limit of small loo

Deusdedit M. Medeiros, R. R. Landim, C. A. S. Almeida

By dimensional reduction of a massive BF theory, a new topological field theory is constructed in (2+1) dimensions. Two different topological terms, one involving a scalar and a Kalb-Ramond fields and another one equivalent to the four-dimensional BF term, are present. We constructed two actions with these topological terms and show that a topological mass g

Fedele Lizzi

In this talk, based on work done in collaboration with G. Landi and R.J Szabo, I will review how string theory can be considered as a noncommutative geometry based on an algebra of vertex operators. The spectral triple of strings is introduced, and some of the string symmetries, notably target space duality, are discussed in this framework.

Bert Schroer

Some of the consequences of Eyvind Wichmann&#39;s contributions to modular theory and the QFT phase-space structure are presented. In order to show the power of those ideas in contemporary problems, I selected the issue of algebraic holography as well as a new nonperturbative constructive approach (based on the modular structur of wedge-localized algebras an

Dmitri Kharzeev, Robert D. Pisarski

The collisions of large nuclei at high energies could produce metastable vacua which are odd under parity, P, charge conjugation, C, and/or CP. Using only the three-momenta of charged pions (or kaons), we show how to construct global observables which are odd under P, C, and CP, and which can be measured on an event by event basis. Model dependent estimates

Markus Wobisch

A QCD analysis of jet production in deep-inelastic scattering is presented. The studies are based on recent measurements of jet cross sections in the H1 experiment at HERA which are directly sensitive to the gluon density in the proton. The inclusion of H1 data on the inclusive deep-inelastic scattering cross section enables us to perform a consistent, simul

M. Bleicher, S. A Bass, H. Stöcker, W. Greiner

The Ultra-relativistic Quantum-Molecular-Dynamics model (UrQMD) is used to study central Pb+Pb reactions at RHIC ($\sqrt{s}=200$ AGeV). The computed collision spectrum reveals that the major part (approx. 80%) of the dynamics is governed by interactions below $\sqrt{s}=100$ GeV. Rapidity spectra of net-baryons (Protons, Hyperons) and produced particles (Pion

Shaaban Khalil, Qaisar Shafi

We consider several low energy consequences arising from a class of supersymmetric models based on the gauge groups $SU(2)_L\times SU(2)_R \times U(1)_{B-L}$ and $SU(4)_C\times SU(2)_L \times SU(2)_R$ in which the gauge hierarchy and $μ$ problems have been resolved. There are important constraints on the MSSM parameters $\tan β(\simeq m_t/m_b)$, $B$ and $μ$,

P. Zenczykowski

Coupled-channel final-state-interaction effects for D and B weak decays into ππand K \bar{K} are discussed in a Regge framework. It is found that the inclusion of coupled-channel effects significantly affects the results obtained previously in a quasi-elastic approximation. It is also shown that in the isospin I=0 channel the inelastic final-state transition

D. J. Miller, S. Moretti

We assess the possibility of measuring the trilinear self-coupling of the Standard Model Higgs boson at future electron-positron linear colliders with centre-of-mass energies between 500 and 1500 GeV. We consider rather light Higgs scalars, with mass below the W+W- threshold, produced in the double Higgs-strahlung channel e+e- -> HHZ and decaying via the dom

André Martin

We show how the combination of analyticity properties derived from local field theory and the unitarity condition (in particular positivity) leads to non-trivial physical results, including the proof of the &#34;Froissart bound&#34; from first principles and the existence of absolute bounds on the pion-pion scattering amplitude.

Eung Jin Chun, Hang Bae Kim

We point out that the axino predicted as the supersymmetric partner of the axion is a good candidate for the recently proposed sterile neutrino cool dark matter. The axino mass falls into the right range in the context of gauge mediated supersymmetry breaking. A sizable mixing of the axino with active neutrinos arises when R-parity violation is allowed and t

M. G. Mustafa, A. Sch&#34;afer, M. H. Thoma

A calculation of the thermal quark propagator is presented taking the gluon condensate above the critical temperature into account. The quark dispersion relation and the dilepton production following from this propagator are derived.

A. Bialas, J. Czyzewski

Multivariate density moments (correlators) of arbitrary order are obtained for the multiplicative self-similar cascade. This result is based on the calculation by Greiner, Eggers and Lipa (reference [1]) where the correlators of the logarithms of the particle densities have been obtained. The density correlators, more suitable for comparison with multipartic

Antonio L. Maroto

We study the production of gravitinos during the preheating era after inflation by means of the non-perturbative Bogolyubov technique. Considering only the helicity $\pm 3/2$ states, the problem is reduced to the simpler Dirac fermions case. We calculate the production in a particular supergravity model in an expanding universe and obtain the spectrum and nu

S. B. Gerasimov

The phenomenological sum-rule-based approach is used to discuss the quark composition dependence of some static electroweak characteristics of baryons.The role of nonvalence degrees of freedom (the sea partons and/or peripheral meson currents) is shown to be important to select and make use of the relevant symmetry parametrization of baryon observables.The i

Seungwon Baek, Yeong Gyun Kim

We derive the upper bounds on certain products of R-parity- and lepton-flavor-violating couplings from $B^\pm \to l^\pm ν$ decays. These modes of B-meson decays can constrain the product combinations of the couplings with one or more heavy generation indices which are comparable with or stronger than the present bounds. And we investigate the possible effect

M. N. Dubinin, H. S. Song

Event characteristics of $W$ boson production at HERA collider are untrivial and sensitive to the production mechanisms. We analyse the distributions of the four particle final state defined by the complete set of $W$ producing perturbative leading order diagrams in the Standard Model and its extension with the anomalous effective lagrangian in the gauge sec

S. J. Brodsky, C. Merino, J. R. Pelaez

We present a general method for extracting the Gell Mann-Low logarithmic derivative of an effective charge of an observable directly from data as a mean for empirically verifying the universal terms of the QCD $β$-function. Our method avoids the biases implicit in fitting to QCD-motivated forms as well as the interpolation errors introduced by constructing d

P. A. Baikov

The systematic approach to solving the recurrence relations for multi-loop integrals is described. In particular, the criteria of their reducibility is suggested.

Marina Artuso

We review some recent results on b decays relevant to future CP violation studies. In particular, some new data on rare hadronic B decays will be presented, as well as inclusive searches for evidence for gluonic penguins and first hints of final state interaction phases in B decays to D* rho. The results discussed are based on data collected by the CLEO expe

Chao-Hsi CHANG

The most important advances achieved recently on the double heavy flavored mesons are reviewed. Some problems and outlooks on them are also outlined.

Cosmin Macesanu, Lynne H. Orr

In this talk we present results of an exact calculation of gluon radiation in top production and decay at lepton colliders, including all spin correlations and interferences. We compare properties of gluons radiated in the production and decay stages and investigate the sensitivity of interference effects to the top decay width.

K. Rummukainen

External (hyper)magnetic field can modify the phase structure in U(1) gauge+Higgs (Landau-Ginzburg) and SU(2)xU(1) gauge+Higgs (Standard Model) theories. In this talk I discuss how the magnetic field can be implemented on the lattice, and summarize the effects on symmetry breaking phase transitions.

Eva-Maria Kabuss

New experiments in polarised deep inelastic scattering will mainly concentrate on the measurement of semi-inclusive asymmetries. Especially, the upgraded HERMES experiment at DESY and the newly build COMPASS experiment at CERN will investigate the gluon polarisation via open charm and high p_T hadron pair production, study in detail the flavour decomposition

Bernhard Haisch, Alfonso Rueda

We report on the progress of a NASA-funded study being carried out at the Lockheed Martin Advanced Technology Center in Palo Alto and the California State University in Long Beach to investigate the proposed link between the zero-point field of the quantum vacuum and inertia. It is well known that an accelerating observer will experience a bath of radiation

C. Gundlach, J. M. Martin-Garcia

Small non-spherical perturbations of a spherically symmetric but time-dependent background spacetime can be used to model situations of astrophysical interest, for example the production of gravitational waves in a supernova explosion. We allow for perfect fluid matter with an arbitrary equation of state p=p(rho,s), coupled to general relativity. Applying a

Alfonso Rueda, Hiroki Sunahata, Bernhard Haisch

For over twenty years the possibility that the electromagnetic zero point field (ZPF) may actively accelerate electromagnetically interacting particles in regions of extremely low particle density (as those extant in intergalactic space (IGS) with n < 1 particle/m^3 has been studied and analyzed. This energizing phenomenon has been one of the few contenders

R. B. Mann, D. Robbins, T. Ohta

We develop the canonical formalism for a system of $N$ bodies in lineal gravity and obtain exact solutions to the equations of motion for N=2. The determining equation of the Hamiltonian is derived in the form of a transcendental equation, which leads to the exact Hamiltonian to infinite order of the gravitational coupling constant. In the equal mass case ex

Juergen Ehlers, Ezra T. Newman

This is intended as an introduction to and review of the work of V, Arnold and his collaborators on the theory of Lagrangian and Legendrian submanifolds and their associated maps. The theory is illustrated by applications to Hamilton-Jacobi theory and the eikonal equation, with an emphasis on null surfaces and wavefronts and their associated caustics and sin

Sukanta Bose, Sanjeev V. Dhurandhar, Archana Pai

We formulate the data analysis problem for the detection of the Newtonian coalescing-binary signal by a network of laser interferometric gravitational wave detectors that have arbitrary orientations, but are located at the same site. We use the maximum likelihood method for optimizing the detection problem. We show that for networks comprising of up to three

Sukanta Bose, Naresh Dadhich

We study a recently proposed horizon defining identity for certain black hole spacetimes. It relates the difference of the Brown-York quasilocal energy and the Komar charge at the horizon to the total energy of the spacetime. The Brown-York quasilocal energy is evaluated for some specific choices of spacetime foliations. With a certain condition imposed on t

Jacob D. Bekenstein

Quantum buoyancy has been proposed as the mechanism protecting the generalized second law when an entropy--bearing object is slowly lowered towards a black hole and then dropped in. We point out that the original derivation of the buoyant force from a fluid picture of the acceleration radiation is invalid unless the object is almost at the horizon, because o

Motomu Tsuda

We generalize the Lagrangian of N = 1 supergravity (SUGRA) by using an arbitrary parameter $ξ$, which corresponds to the inverse of Barbero&#39;s parameter $β$. This generalized Lagrangian involves the chiral one as a special case of the value $ξ= \pm i$. We show that the generalized Lagrangian gives the canonical formulation of N = 1 SUGRA with the real Ash

Yeong E. Kim, Alexander L. Zubarev

This paper reports a detailed description of the equivalent linear two-body method for the many body problem, which is based on an approximate reduction of the many-body Schroedinger equation by the use of a variational principle. To test the accuracy of the method it has been applied to the one-dimensional N-body problem with pair-wise contact interactions

Fei Zhou

A theory of mesoscopic fluctuations in disordered thin superconducting films in a parallel magnetic field is developed. At zero temperature, the superconducting state undergoes a phase transition into a state characterized by superfluid densities of random signs, instead of a spin polarized disordered Fermi liquid phase. Consequently, the ground state belong

J. Ashkenazi

The electronic structure of the high-T_c cuprates is studied on the basis of both &#34;large-U&#34; and &#34;small-U&#34; orbitals. A striped structure is obtained, and three types of carriers: polaron-like &#34;stripons&#34; carrying charge, &#34;quasielectrons&#39;&#39; carrying charge and spin, and &#34;svivons&#34; carrying spin and lattice distortion. A

M. Ershov, H. Ruda, A. Shik, A. G. U. Perera

A theory of the transient spectroscopy of quantum well (QW) structures under a large applied bias is presented. An analytical model of the initial part of the transient current is proposed. The time constant of the transient current depends not only on the emission rate from the QWs, as is usually assumed, but also on the subsequent carrier transport across

G. Litak, B. L. Gyorffy

In case of superconductors whose electrons attract each other only if they are near certain centers, the question arises &#39;How many such centers are needed to make the ground state superconducting?&#39; We shall examine it in the context of a random U Hubbard model. In short we study the case where U_i is -|U| and 0 with probability c and 1-c respectively

Th. Maier, M. Jarrell, Th. Pruschke, J. Keller

We develop a Non-Crossing Approximation (NCA) for the effective cluster problem of the recently developed Dynamical Cluster Approximation (DCA). The DCA technique includes short-ranged correlations by mapping the lattice problem onto a self-consistently embedded periodic cluster of size $N_c$. It is a fully causal and systematic approximation to the full lat

Igor I. Smolyaninov, Chi H. Lee, Christopher C. Davis

We report observation of strongly enhanced surface SHG in BaTiO_3 due to excitation of a photorefractive surface electromagnetic wave. Surface SH intensity may reach 10^{-2} of the incident fundamental light intensity. Angular, crystal orientation and polarization dependencies of this SHG are presented. Possible applications of this effect in nonlinear surfa

M. v. Zimmermann, T. Frello, N. H. Andersen, J. Madsen

High energy x-ray diffraction is used to investigate the bulk oxygen ordering properties of YBa_2Cu_3O_{6+x}. Superstructures of Cu-O chains aligned along the b axis and ordered with periodicity ma, along the a axis have been observed. For $x < 0.62$ the only observed superstructure is ortho-II with m=2. At room temperature we find ortho-III (m=3) for $0.72\

L. You, M. Marinescu

We present theoretical prospects for creating p-wave paired BCS states of magnetic trapped fermionic atoms. Based on our earlier proposal of using dc electric fields to control both the strength and anisotropic characteristic of atom-atom interaction and our recently completed multi-channel atomic collision calculations we discover that p-wave pairing with $

V. A. Luchnikov, N. N. Medvedev, Yu. I. Naberukhin, H. R. Schober

We combine a conventional harmonic analysis of vibrations in a one-atomic model glass of soft spheres with a Voronoi-Delaunay geometrical analysis of the structure. ``Structure potentials&#39;&#39; (tetragonality, sphericity or perfectness) are introduced to describe the shape of the local atomic configurations (Delaunay simplices) as function of the atomic

Marc Barthelemy, Luis A. N. Amaral

We correct the value of the exponent τ.

Jort van Mourik

We introduce $\infty$-dimensional versions of three common models of random hetero-polymers, in which both the polymer density and the density of the polymer-solvent mixture are finite. These solvable models give valuable insight into the problems related to the (quenched) average over the randomness in statistical mechanical models of proteins, without havi

Christian Knetter, Goetz S. Uhrig

The flow equation method (Wegner 1994) is used as continuous unitary transformation to construct perturbatively effective Hamiltonians. The method is illustrated in detail for dimerized and frustrated antiferromagnetic S=1/2 chains. The effective Hamiltonians conserve the number of elementary excitations which are S=1 magnons for the dimerized chains. The se

I. V. Ponomarev, V. V. Flambaum, A. L. Efros

We calculate the singlet-triplet splitting for a couple of two-dimensional electrons in the potential of two positively charged impurities which are located out of plane. We consider different relations between vertical distances of impurities $h_1$ and $h_2$ and their lateral distance $R$. Such a system has never been studied in atomic physics but the metho

H. Kleinert, A. Chervyakov, B. Hamprecht

Recently developed strong-coupling theory open up the possibility of treating quantum-mechanical systems with hard-wall potentials via perturbation theory. To test the power of this theory we study here the exactly solvable quantum mechanics of a point particle in a one-dimensional box. Introducing an auxiliary harmonic mass term $m$, the ground-state energy

A. Koga, S. Kumada, N. Kawakami

Quantum phase transitions between the magnetically ordered and disordered states are studied for the two-dimensional antiferromagnetic quantum spin systems with ladder, plaquette, and mixed-spin structures. Starting with properly chosen singlet-cluster configurations, we perform the series expansion for the staggered magnetic susceptibility. The phase bounda

S. I. Vedeneev, A. G. M. Jansen, B. A. Volkov, P. Wyder

Magnetoresistance (MR) in the out-of-plane resistivity $ρ_c$ for the normal state of the one-layer high-quality Bi_2Sr_2CuO_x single crystals under various dc magnetic fields up to 28 T over the temperature region 6-100 K has been measured. We observed the anomalously large negative longitudinal MR up to 60%. At low temperatures the normal-state MR in contra

David W. Brown, Aldo H. Romero, Katja Lindenberg

We apply the Merrifield variational method to the Holstein molecular crystal model in D dimensions to compute non-adiabatic polaron band energies and Franck-Condon factors at general crystal momenta. We analyze these observable properties to extract characteristic features related to polaron self-trapping and potential experimental signatures. These results

Xiao Hu

The present approach takes into account thermal fluctuations both in the rotation of SO(5) superspins between the AF and SC subspaces, and in the phase variables of SC order parameters. Temperature vs. g-field phase diagrams for null external magnetic field are presented, where the g field is conjugate with the quadratic order parameters and breaks the SO(5)

Marek Hytha, Antonin Simunek

In this paper there is presented method for ab initio calculation of the phonon spectra. The method is based upon a direct calculation of the dynamical matrix via second derivatives of the total energy. The pseudopotential technique in plane-wave basis set was used to calculate the total energy within the local density approximation (LDA). For the change of

Bernard Derrida, Jesper Lykke Jacobsen, Reuven Zeitak

We calculate, using numerical methods, the Lyapounov exponent gamma(E) and the density of states rho(E) at energy E of a one-dimensional non-Hermitian Schroedinger equation with off-diagonal disorder. For the particular case we consider, both gamma(E) and rho(E) depend only on the modulus of E. We find a pronounced maximum of rho(|E|) at energy E=2/sqrt(3),

A. Marrone, A. D. Polosa, G. Scioscia, S. Stramaglia

We describe the multiresolution wavelet analysis of blood pressure waves in vasovagal syncope-affected patients compared with those in healthy people, using Haar and Gaussian bases. A comparison between scale-dependent and scale-independent measures discriminating the two classes of subjects is made. What emerges is a sort of equivalence between these two me

Brian Møller Andersen, Henrik Bruus, Per Hedegård

We study the fermionic states of the antiferromagnetically ordered vortex cores predicted to exist in the superconducting phase of the newly proposed SO(5) model of strongly correlated electrons. Our model calculation gives a natural explanation of the recent STM measurements on BSCCO, which in surprising contrast to YBCO revealed completely insulating vorte