arXiv papers from November 1996

V. Kataev, B. Rameev, B. Buechner, M. Huecker

Measuring the ESR of Gd spin probes we have studied the magnetic properties of the copper oxide planes in the low temperature tetragonal (LTT) phase of Eu doped La_{2-x}Sr_xCuO_4. The data give evidence that at particular levels of Sr and Eu doping the frequency of the antiferromagnetic fluctuations in the LTT phase dramatically decreases at low temperatures

D. Kharzeev, C. Lourenco, M. Nardi, H. Satz

Data from J/psi and psi' production in p-A collisions are used to determine the cross section for absorption of pre-resonance charmonium in nuclear matter. The J/psi suppression in O-Cu, O-U and S-U collisions is fully reproduced by the corresponding nuclear absorption, while Pb-Pb collisions show an additional suppression increasing with centrality. We stud

Vladimir I. Man'ko, Alfred Wünsche

The photon distribution function of a discrete series of excitations of squeezed coherent states is given explicitly in terms of Hermite polynomials of two variables. The Wigner and the coherent-state quasiprobabilities are also presented in closed form through the Hermite polynomials and their limiting cases. Expectation values of photon numbers and their d

V. I. Man'ko, G. Marmo, E. C. G. Sudarshan, F. Zaccaria

It is shown, that for quantum systems the vectorfield associated with the equations of motion may admit alternative Hamiltonian descriptions, both in the Schr\"odinger and Heisenberg pictures. We illustrate these ambiguities in terms of simple examples.

J. Schmidt-Sorensen, T. Csorgo

A fully interactive database is presented, which provides user-friendly access to experimental results on single-particle spectra and two-particle correlations (particle interferometry or HBT-effect). The database is available on the World-Wide-Web at: http://www.quark.lu.se/~janus/hbt_home.html .

V. I. Man'ko, G. Marmo, E. C. G. Sudarshan, F. Zaccaria

The notion of f-oscillators generalizing q-oscillators is introduced. For classical and quantum cases, an interpretation of the f-oscillator is provided as corresponding to a special nonlinearity of vibration for which the frequency of oscillation depends on the energy. The f-coherent states (nonlinear coherent states) generalizing q-coherent states are cons

S. Mancini, V. I. Man'ko, P. Tombesi

It is shown that because of the radiation pressure a Schr\"odinger cat state can be generated in a resonator with oscillating wall. The optomechanical control of quantum macroscopic coherence and its detection is taken into account introducing new cat states. The effects due to the environmental couplings with this nonlinear system are considered developing

Enzo Marinari

I discuss optimized data analysis and Monte Carlo methods. Reweighting methods are discussed through examples, like Lee-Yang zeroes in the Ising model and the absence of deconfinement in QCD. I discuss reweighted data analysis and multi-hystogramming. I introduce Simulated Tempering, and as an example its application to the Random Field Ising Model. I illust

N. P. Merenkov

Analytical method is applied for description of the small angle Bhabha scattering at LEP1. Inclusive event selection for asymmetrical wide-narrow circular detectors is considered. The QED correction to the Born cross-section is calculated with leading and next-to-leading accuracy in the second order of perturbation theory and with leading one --- in the thir

H. K. Janssen

A general field theoretic model of directed percolation with many colors that is equivalent to a population model (Gribov process) with many species near their extinction thresholds is presented. It is shown that the multicritical behavior is always described by the well known exponents of Reggeon field theory. In addition this universal model shows an insta

S. Krompiewski, M. Zwierzycki, U. Krey

It is shown that the current-perpendicular-to-plane giant magneto-resistance (CPP-GMR) oscillations, in the ballistic regime, are strongly correlated with those of the exchange coupling (J). Both the GMR and J are treated on equal footing within a rigorously solvable tight-binding single-band model. The strong correlation consists in sharing asymptotically t

O. G. Tchikilev

It is shown that charged hadron multiplicity distributions in restricted (pseudo)rapidity intervals in e+e- annihilation and in e+p scattering at HERA are quite well described by the modified negative binomial distribution and its simple extension.

O. G. Tchikilev

It is shown that charged hadron multiplicity distributions in lepton-nucleon scattering are fairly well described by the modified negative binomial distribution in the energy range from 3-4 to 220 GeV. The energy behaviour of the parameter k is similar to the dependence observed for e+e- annihilation.

J. J. Blanco-Pillado, R. A. Vázquez, E. Zas

We obtain the horizontal air shower rate from the (EeV) high energy neutrino flux predicted in some topological defect scenarios as the source for the highest energy cosmic rays. Emphasis is made on the different character of the events depending on the neutrino flavor an type of interaction. We show that the bound for muon poor showers in the $10^5-10^7$ Ge

S. F. Hewson, M. J. Perry

We discuss supersymmetry in twelve dimensions and present a covariant supersymmetric action for a brane with worldsheet signature (2,2), called a super (2+2)-brane, propagating in the osp(64,12) superspace. This superspace is explicitly constructed, and is trivial in the sense that the spinorial part is a trivial bundle over spacetime, unlike the twisted sup

Stefano Mancini, Paolo Tombesi, Vladimir I. Manko

We provide a simple analytic relation which connects the density operator of the radiation field with the number probabilities. The problem of experimentally "sampling" a general matrix elements is studied, and the deleterious effects of nonunit quantum efficiency in the detection process are analyzed showing how they can be reduced by using the squeezing te

J. M. Moreno, D. H. Oaknin, M. Quiros

Electric charge and color breaking minima along third generation squark directions do appear in the Minimal Supersymmetric Standard Model for particular regions of the corresponding supersymmetric parameters $A_t$, $\mu$, $\tan\beta$, $m_Q^2$ and $m_U^2$. We have studied possible instabilities of electroweak sphalerons along non-trivial squark configurations

Peter Leifer

A underlying dynamical structure for both relativity and quantum theory-``superrelativity'' has been proposed in order to overcome the well known incompatibility between these theories. The relationship between curvature of spacetime (gravity) and curvature of the projective Hilbert space of pure quantum states is established as well.

J. M. Tranquada, P. Wochner, D. J. Buttrey

Inelastic neutron scattering has been used to measure the low-energy spin excitations in the ordered charge-stripe phase of La(2)NiO(4+d) with d=0.133. Spin-wave-like excitations disperse away from the incommensurate magnetic superlattice points with a velocity ~60% of that in the d=0 compound. Incommensurate inelastic peaks remain well-resolved up to at lea

Elizabeth Jenkins

The large value of the top quark mass implies that the rare top decays $t \rightarrow b W^+ Z, s W^+ Z$ and $d W^+ Z$, and $t \rightarrow c W^+ W^-$ and $u W^+ W^-$, are kinematically allowed decays so long as $m_t \ge m_W + m_Z + m_{d_i} \approx 171.5 GeV + m_{d_i}$ or $m_t \ge 2m_W + m_{u,c} \approx 160.6 GeV + m_{u,c}$, respectively. The partial decay wid

Y. Anusooya, Swapan K. Pati, S. Ramasesha

We report the symmetrized density matrix renormalization group (DMRG) study of neutral and doped oligomers of PPP system within an extended Hubbard model. Model parameters are determined by comparing the existing results for interacting small system. We compute a number of properties in the ground state as well as in the one-photon, two-photon and triplet st

David Schade, L. Felipe Barrientos, Omar Lopez-Cruz

Two-dimensional surface photometry derived from Hubble Space Telescope imaging is presented for a sample of 225 early-type galaxies (assumed to be cluster members) in the fields of 9 clusters at redshifts $0.17 < z < 1.21$. The 94 luminous ellipticals ($M_{AB}(B)<-20$; selected by morphology alone with no reference to color) form tight sequences in the size-

J. C. A. Barata, F. Nill

We construct dyonic states in 2+1-dimensional lattice Z_N-Higgs models, i.e., states which are both, electrically and magnetically charged. The associated Hilbert spaces carry charged representations of the observable algebra, the global transfer matrix and a unitary implementation of the group of spatial lattice translations. We prove that for coinciding to

Giovannni Gallavotti, David Ruelle

Nonequilibrium statistical mechanics close to equilibrium is studied using SRB states and a formula for their derivatives with respect to parameters. We write general expressions for the thermodynamic fluxes (or currents) and the transport coefficients, generalizing previous results. In this framework we give a general proof of the Onsager reciprocity relati

V. A. De Lorenci, N. F. Svaiter

We investigate how a uniformly rotating frame is defined as the rest frame of an observer rotating with constant angular velocity $\Omega$ around the $z$ axis of an inertial frame. Assuming that this frame is a Lorentz one, we second quantize a free massless scalar field in this rotating frame and obtain that creation-anihilation operators of the field are n

K. Yabana, G. F. Bertsch

We apply the time-dependent local density approximation (TDLDA) to calculate dipole excitations in small carbon clusters. A strong low-frequency mode is found which agrees well with observation for clusters C_n with n in the range 7-15. The size dependence of the mode may be understood simply as the classical resonance of electrons in a conducting needle. Fo

D. V. Antonov

Under certain conditions, imposed on the viscosity of the fluid, initial data and the class of contours under consideration, the Cauchy problem with finite values of time for the loop equation in turbulence with Gaussian random forces is solved by making use of the smearing procedure for the loop space functional Laplacian. The solution obtained depends on t

M. Vergassola, M. Avellaneda

Transport of scalar fields in compressible flow is investigated. The effective equations governing the transport at scales large compared to those of the advecting flow are derived by using multi-scale techniques. Ballistic transport generally takes place when both the solenoidal and the potential components of the velocity do not vanish, despite of the fact

S. V. Levonian

Until the mystery of confinement is understood from the first principles, so called `soft physics' remains an important area of research, providing valuable information on underlying dynamics of strong interactions at long distances. In this short review an attempt is made to summarize recent experimental results on multiparticle production in e+e- annihilat

Ph. Jacquod, D. L. Shepelyansky

We study numerically the interaction and disorder effects for two quasiparticles in two and three dimensions. The dependence of the interaction-induced Breit-Wigner width on the excitation energy above the Fermi level, the disorder strength and the system size is determined. A regime is found where the width is practically independent of the excitation energ

Miguel A. Sanchis-Lozano

Effective fields defined in the heavy-quark effective theory to describe heavy quarks in heavy-light hadrons are examined in some detail in the standard formulation of a quantum field theory.

John Ellis

Some of the hot topics in neutrino physics are discussed, with particular emphasis on neutrino oscillations. After proposing credibility criteria for assessing various claimed effects, particular stress is laid on the solar neutrino deficit, which seems unlikely to have an astrophysical explanation. Comments are also made on the possibility of atmospheric ne

Chris Mihos, Stacy McGaugh, Erwin de Blok

We demonstrate that, due to their low surface mass density and large dark matter content, LSB disks are quite stable against the growth of global bar modes. However, they may be only marginally stable against local disk instabilities. We simulate a collision between an LSB and HSB galaxy and find that, while the HSB galaxy forms a strong bar, the response of

Anne-Christine Davis, Warren B. Perkins

Grand unified theories can admit cosmic strings with fermion zero modes which result in the string carrying a current and the formation of stable remnants, vortons. We consider theories in which the zero modes do not survive a subsequent phase transition, for example the electroweak transition, resulting in vorton dissipation. The dissipating vortons can cre

Youngsoo Yoon, Yongsung Yoon

The asymptotic conformal invariance of some SU(2) model and Standard Model in curved space-time are investigated. We have examined the conditions for asymptotic conformal invariance for these models numerically.

Byung Deok Yu, Matthias Scheffler

Using the plane wave pseudopotential method we performed density functional theory calculations on the stability of steps and self-diffusion processes on Ag(100). Our calculated step formation energies show that the {111}-faceted step is more stable than the {110}-faceted step. In accordance with experimental observations we find that the equilibrium island

D. Comelli, J. Bernabeu, A. Pich, A. Santamaria

Non-decoupling effects related to a large $m_t$ affecting non-oblique radiative corrections in vertices ($Z\bar{b}b$) and boxes ($B$-$\bar{B}$ mixing and $\epsilon_K$) are very sensitive to the particular mechanism of spontaneous symmetry breaking. We analyze these corrections in the framework of a chiral electroweak standard model and find that there is onl

Mairi Sakellariadou

Doppler peaks in the cosmic microwave background may allow us to distinguish among the two classes of theories-inflationary models and topological defect scenarios-which attempt to explain the origin of structure formation in the universe. We consider density perturbations seeded by global textures in a universe dominated by cold dark matter. We calculate th

E. Pehlke, N. Moll, M. Scheffler

The formation of dislocation-free three-dimensional islands during the heteroepitaxial growth of lattice-mismatched materials has been observed experimentally for several material systems. The equilibrium shape of the islands is governed by the competition between the surface energy and the elastic relaxation energy of the islands as compared to the uniform

David J. Toms

A simple pedagogical introduction to the effective action method of quantum field theory is given at a level suitable for beginning postgraduate students. It is shown how to obtain the effective potential at zero temperature from a regularized zero-point energy. The results are applicable to curved as well as to flat space. The generalization to finite tempe

M. Pietroni, N. Rius, N. Tetradis

We discuss the question of inverse symmetry breaking at non-zero temperature using the exact renormalization group. We study a two-scalar theory and concentrate on the nature of the phase transition during which the symmetry is broken. We also examine the persistence of symmetry breaking at temperatures higher than the critical one.

Peter Prelovsek

The electron Green's functions $G({\bf k},\omega)$ within the t-J model and in the regime of intermediate doping is studied analytically using equations of motion for projected fermionic operators and the decoupling of the self energy into the single-particle and spin fluctuations. It is shown that the assumption of marginal spin dynamics at T=0 leads to an

Takashi Nakatsukasa, Yoshifumi R. Shimizu

We propose a simple and systematic method to quantize the cranking model and to calculate the matrix elements of intrinsic operators entering the generalized intensity relations. An example of the application is given to show the Coriolis coupling effects for B(E3) values of the 3- octupole states in Gd isotopes.

Takashi Nakatsukasa, Kenichi Matsuyanagi, Shoujirou Mizutori, Yoshifumi R. Shimizu

Microscopic RPA calculations based on the cranked shell model are performed to investigate the quadrupole and octupole correlations for excited superdeformed (SD) bands in even-even A=190 nuclei. The K=2 octupole vibrations are predicted to be the lowest excitation modes at zero rotational frequency. The Coriolis coupling at finite frequency produces differe

A. A. Penin, A. A. Pivovarov

We discuss the ways of extracting a low energy scale of an underlying theory using high energy scattering data. Within an exactly solvable model of quantum mechanics we analyze a technique based on introduction of nonperturbative power corrections accounting for asymptotically small terms and an alternative approach exploiting a modified running coupling con

R. Bergamini, P. Sedici, P. Verrocchio

The influence of Inflation on initial (i.e. at Planck's epoch) large anisotropy of the Universe is studied, considering a more general metric than the isotropic one: the locally rotationally symmetric (L.R.S.) Bianchi IX metric. We find, then, a large set of initial conditions of intrinsic curvature and shear allowing an inflationary epoch that make the anis

D. Bardin, L. Kalinovskaya, T. Riemann

We calculate cross-sections for neutral current deep inelastic scattering at HERA with photon tagging. Both the exact lowest-order cross-section and a leading logarithmic approximation of next-order corrections are calculated. The latter amounts to less than 20% in a large kinematical range. The integrations are performed numerically but without relying on M

John Ellis, Marek Karliner, Mark. A. Samuel

We predict that the four-loop contribution \beta_3 to the QCD \beta function in the MS-bar prescription is given by \beta_3\simeq 23,600(900) - 6,400(200) N_f + 350(70) N_f^2 + 1.5 N_f^3, where N_f is the number of flavours and the coefficient of N_f^3 is an exact result from large-N_f expansion. In the phenomenologically-interesting case N_f=3, we estimate

R. Turolla, S. Zane, A. Treves, A. Illarionov

As first shown by Shvartsman (1970), a neutron star accreting close to the Eddington limit must acquire a positive charge in order for electrons and protons to move at the same speed. The resulting electrostatic field may contribute to accelerating positrons produced near the star surface in conjunction with the radiative force. We reconsider the balance bet

Carlos Castro

First steps in incorporating Nottale's scale-relativity principle to string theory and extended objects are taken. Scale Relativity is to scales what motion Relativity is to velocities. The universal, absolute, impassible, invariant scale under dilatations, in Nature, is taken to be the Planck scale which is not the same as the string scale. Starting with Na

E. N. M. Cirillo, G. Gonnella, A. Pelizzola

The critical and multicritical behavior of the simple cubic Ising model with nearest-neighbor, next-nearest-neighbor and plaquette interactions is studied using the cube and star-cube approximations of the cluster variation method and the recently proposed cluster variation--Pad\'e approximant method. Particular attention is paid to the line of critical end

A. B. Arbuzov, G. I. Gach, V. Yu. Gontchar, E. A. Kuraev

Analytical formulae for small-angle Bhabha scattering cross-section at LEP1 are given for the case of wide-narrow angular acceptance. Inclusive and calorimeter event selections are considered. Numerical results are presented.

H. -D. Doebner, P. Nattermann

In this contribution we review results on the kinematics of a quantum system localized on a connected configuration manifold and compatible dynamics for the quantum system including external fields and leading to non-linear Schr\"odinger equations for pure states.

Lu-Ming Duan, Guang-Can Guo

Decoherence in quantum computer memory due to the inevitable coupling to the external environment is examined. We take the assumption that all quantum bits (qubits) interact with the same environment rather than the assumption of separate environments for different qubits. It is found that the qubits are decohered collectively. For some kinds of entangled in

Samar Abbas, Afsar Abbas

Extraterrestrial processes like neutrinos from collapsing stars, cosmic rays from supernovae and cosmic rays from neutron star mergers etc. have recently been proposed as models to explain the periodic mass extinctions such as that which wiped out the dinosaurs at the K-T boundary. Here we show that these models fail to give any reasonable explanation of sev

JungJai Lee

We comment on the regularization of the expectation values of Wilson surfaces for the bosonic string in the (3+1) dimensions. We analyze the singular behaviors of propagator for the Chern-Simons action with the additional higher order terms.

K. Saito, K. Tsushima, A. W. Thomas

The quark-meson coupling model, based on a mean-field description of non-overlapping nucleon bags bound by the self-consistent exchange of $\sigma$, $\omega$ and $\rho$ mesons, is extended to investigate the change of hadron properties in finite nuclei. Relativistic Hartree equations for spherical nuclei have been derived from a relativistic quark model of t

J. A. Sidles

This article describes the AC Stark, Stern-Gerlach, and Quantum Zeno effects as they are manifested during continuous interferometric measurement of a two-state quantum system (qubit). A simple yet realistic model of the interferometric measurement process is presented, and solved to all orders of perturbation theory in the absence of thermal noise. The stat

A. Frank, R. Lemus, R. Bijker, F. Perez-Bernal

We apply a symmetry-adapted algebraic model to the vibrational excitations in D_3h and T_d molecules. A systematic procedure is used to establish the relation between the algebraic and configuration space formulations. In this way we have identified interaction terms that were absent in previous formulations of the vibron model. The inclusion of these new in

S. Lukyanov, A. Zamolodchikov

We propose an explicit expression for vacuum expectation values of the exponential fields in the sine-Gordon model. Our expression agrees both with semi-classical results in the sine-Gordon theory and with perturbative calculations in the Massive Thirring model. We use this expression to make new predictions about the large-distance asymptotic form of the tw

Michael Harris

Let F be a p-adic field and n a positive integer. The local Langlands conjecture asserts the existence of a bijection between irreducible admissible representations of GL(n,F) and n-dimensional admissible representations of the Weil-Deligne group of F. This bijection is required to satisfy certain natural compatibilities, of which the most important is compa

Alphonse P. Magnus

We consider orthogonal polynomials p_n with respect to an exponential weight function w(x) = exp(-P(x)). The related equations for the recurrence coefficients have been explored by many people, starting essentially with Laguerre [49], in order to study special continued fractions, recurrence relations, and various asymptotic expansions (G. Freud's contributi

Andreas Blass, Heike Mildenberger

All ultrafilters under consideration here are non-principal ultrafilters on the set omega of natural numbers. We are concerned with the possible cofinalities of ultrapowers of omega with respect to such ultrafilters. We show that no cardinal below the groupwise density number g can occur as such a cofinality and that at most one cardinal below the splitting

Ben Dorman

We consider the general theoretical problem of ultraviolet light from old stellar populations (t > 2 Gyr), and the interpretation of galaxy spectra at short wavelengths (lamda < 3200A) The sources believed to be responsible for the observed `ultraviolet upturn phenomenon&#39; (UVX) are Post-AGB (P-AGB), extreme horizontal branch (EHB) and AGB-Manque (AGBM) s

Edward L. Wright

CMB anisotropy experiments seeking to make maps with more pixels than the 6144 pixels used by the COBE DMR need to address the practical issues of the computer time and storage required to make maps. A simple, repetitive scan pattern reduces these requirements but leaves the experiment vulnerable to systematic errors and striping in the maps. In this paper I

Giorgio Matt

Current ideas on the X-ray spectrum of Compton-thick Seyfert 2 galaxies are reviewed, and a brief description of the four presently known sources belonging to this class are given.

G. Sardanashvily, K. Kirillov

Building on the first variational formula of the calculus of variations, one can derive the energy-momentum conservation laws from the condition of the Lie derivative of gravitation Lagrangians along vector fields corresponding to generators of general covariant transformations to be equal to zero. The goal is to construct these vector fields. In gauge gravi

Eloy Ayón-Beato

The vanishing of the electromagnetic field, for purely electric configurations of spontaneously broken Abelian models, is established in the domain of outer communications of a static asymptotically flat black hole. The proof is gauge invariant, and is accomplished without any dependence on the model. In the particular case of the Abelian Higgs model, it is

John Ellis, Yitzhak Frishman, Amihay Hanany, Marek Karliner

We calculate in QCD$_2$ the ratios of baryonic matrix elements of $\Delta I = 2$ and $\Delta I = 0$ four-fermion operators, with a view to understanding better the mechanism of $\Delta I = 1/2$ enhancement in QCD$_4$. We find relatively small suppressions of both the scalar-scalar and vector-vector $\Delta I = 2$ four-fermion operators. We discuss the possib

G. Dereli, T. Cagin, M. Uludogan, M. Tomak

We utilize the many-body potentials developed by Sutton and Chen(1990) within the context of the tight-binding approach to study the bulk properties of metals and metal alloys in molecular dynamics (MD) simulations. In the simulations of Pt-Rh alloys we used the MD algorithms based on an extended Hamiltonian formalism from the works of Andersen(1980), Parrin

Klaus Behrndt

Intersecting D-brane configurations are related to black holes in D=4. Using the standard way of compactification only the Reissner-Nordstr{\o}m black hole is non-singular. In this paper we argue, that also the other black holes are non-singular if i) we compactify over a periodic array and ii) we allow the string metric after reaching a critical curvature t

Paweł Kunstman, Karol Życzkowski, Jakub Zakrzewski

Statistical properties of parametric motion in ensembles of Hermitian banded random matrices are studied. We analyze the distribution of level velocities and level curvatures as well as their correlation functions in the crossover regime between three universality classes. It is shown that the statistical properties of level dynamics are in general non-unive

SESAM-Collaboration, :, N. Eicker, U. Glässner

We present recent results of SESAM's large scale lattice simulation of QCD with two dynamical flavours of Wilson fermions. The emphasis is on future prospects in the extraction of flavour-singlet matrix elements, i.e the pi-nucleon sigma term, with dynamical configurations.

J. Ambjorn, K. N. Anagnostopoulos, T. Ichihara, L. Jensen

We study a c=-2 conformal field theory coupled to two-dimensional quantum gravity by means of dynamical triangulations. We define the geodesic distance r on the triangulated surface with N triangles, and show that dim[r^{d_H}]= dim[N], where the fractal dimension d_H = 3.58 +/- 0.04. This result lends support to the conjecture d_H = -2\alpha_1/\alpha_{-1}, w

A. Ya. Maltsev

The work is devoted to the proof of the conservation of local field-theoretical Hamiltonian structures in Whitham's method of averaging. The consideration is based on the procedure of averaging of local Poisson bracket, proposed by B.A.Dubrovin and S.P.Novikov. Using the Dirac procedure of restriction of the Poisson bracket on the submanifold in the function

O. Arratia, M. A. Martin, M. A. Olmo

We deduce a kernel that allows the Moyal quantization of the cylinder (as phase space) by means of the Stratonovich-Weyl correspondence.

Jim McElwaine

This paper describes an algorithm for selecting a consistent set within the consistent histories approach to quantum mechanics and investigates its properties. The algorithm uses a maximum information principle to select from among the consistent sets formed by projections defined by the Schmidt decomposition. The algorithm unconditionally predicts the possi

Krastan B. Blagoev, Kevin S. Bedell

One dimensional metals are described by Luttinger liquid theory. Recent experiments have addressed the relation between this non-Fermi liquid behavior and the existence of a Fermi surface. We show that Luttinger's theorem, with few modifications, holds for the one-dimensional Tomonaga-Luttinger model. The implications for the high temperature superconductors

R. S. Markiewicz

The Van Hove singularity (VHS) provides a paradigm for the study of the role of peaks in the density of states (dos) on electronic properties. More importantly, it appears to play a major role in the physics of the high-T_c superconductors, particularly since recent photoemission studies have found that the VHS is close to the Fermi level in most of the high

G. Montagna, O. Nicrosini, F. Piccinini

The ${\cal O} (\alpha^3)$ leading logarithmic contribution to the QED radiator in the additive form is considered. The effect of the correction on two-fermion physics at LEP1 and LEP2 is evaluated and critically compared with the one of next-to-leading ${\cal O} (\alpha^2)$ corrections. A critical comparison with existing estimates for the LEP1 energy range

T. Wong, S. M. Tan, M. J. Collett, D. F. Walls

In a recent experiment by Eichmann et al., polarization-sensitive measurements of the fluorescence from two four-level ions driven by a linearly polarized laser were made. Depending on the polarization chosen, different degrees of interference were observed. We carry out a theoretical and numerical study of this system, showing that the results can largely b

Subrata Bal, K. V. Shajesh, Debabrata Basu

The character problems of SU(2) and SU(1,1) are reexamined from the standpoint of a physicist by employing the Hilbert space method which is shown to yield a completely unified treatment for SU(2) and the discrete series of representations of SU(1,1). For both the groups the problem is reduced to the evaluation of an integral which is invariant under rotatio

Bastian Bergerhoff, Christof Wetterich

Existence and properties of the electroweak phase transition in the early universe depend strongly on the mass of the Higgs scalar M_H. There is presumably no true symmetry restoration at high temperature. Nevertheless, a first order phase transition occurs in the standard model for M_H smaller than about 70 GeV. For a realistic scalar mass M_H larger than a

N. N. Nikolaev, W. Schaefer

We propose two new sources of a substantial tensor polarization of sea partons in the deuteron: the diffractive nuclear shadowing which depends on the alignment of nucleons in the polarized deuteron and the nuclear excess of pions in the deuteron which is sensitive to the spin state of the deuteron. The corresponding tensor structure function $b_{2}(x,Q^{2})

Jae Woo Lee, Vladimir Privman

We introduce a model of three-species two-particle diffusion-limited reactions A+B -> A or B, B+C -> B or C, and C+A -> C or A, with three persistence parameters (survival probabilities in reaction) of the hopping particle. We consider isotropic and anisotropic diffusion (hopping with a drift) in 1d. We find that the particle density decays as a power-law fo

Michael Titov, Daniel Braun, Yan V. Fyodorov

We study numerically and analytically the moments of the dimensionless level curvature for one-dimensional disordered rings of the circumference L pierced by a magnetic flux. The negative moments of the curvature distribution can be evaluated analytically in the extreme localization limit. The ensuing small curvature asymptotic of the corresponding distribut

The New Muon Collaboration

Results are presented for F2d/F2p and Rd-Rp from simultaneous measurements of deep inelastic muon scattering on hydrogen and deuterium targets, at 90, 120, 200 and 280 GeV. The difference Rd-Rp, determined in the range 0.002<x<0.4 at an average Q^2 of 5 GeV^2, is compatible with zero. The x and Q^2 dependence of F2d/F2p was measured in the kinematic range 0.

N. Tetradis

We compare the results of renormalization-group and lattice studies for the properties of the electroweak phase transition. This comparison reveals the mechanisms that underlie the phenomenology of the phase transition.

Jukka A. Ketoja, Indubala I. Satija

The almost periodic eigenvalue problem described by the Harper equation is connected to other classes of quasiperiodic behaviour: the dissipative dynamics on critical invariant tori and quasiperiodically driven maps. Firstly, the strong coupling limit of the supercritical Harper equation and the strong dissipation limit of the critical standard map play equi

Hoang Ngoc Long

The lepton family-number changing \Delta L = 2 neutrino reactions in the framework of the SU(3)_C X SU(3)_L X U(1)_N model with right-handed neutrinos are presented. These processes have a much-enhanced cross section as a result of s-channnel resonant bilepton Y production and they should be added to ultrahigh-energy neutrino interactions.

N. Sakai

Supersymmetric Yang-Mills theories are considered in 1+1 dimensions. Firstly physical mass spectra of supersymmetric Yang-Mills theories in 1+1 dimensions are evaluated in the light-cone gauge with a compact spatial dimension. The supercharges are constructed in order to provide a manifestly supersymmetric infrared regularization for the discretized light-co

N. Sakai

After briefly reviewing the nonperturbative dynamics of N=1 supersymmetric field theories, soft SUSY breaking mass terms are introduced into the SUSY gauge theories and their effects on gauge symmetry breaking pattern are studied. For $N_f<N_c$, we include the dynamics of the non-perturbative superpotential and use the original (s)quark and gauge fields. For

J. Magnen, G. Poirot, V. Rivasseau

In this paper we describe a strategy to study the Anderson model of an electron in a random potential at weak coupling by a renormalization group analysis. There is an interesting technical analogy between this problem and the theory of random matrices. In d=2 the random matrices which appear are approximately of the free type well known to physicists and ma

Y. Sirois

Searches at the e-p collider HERA for supersymmetric partners of the Standard Model fermions are presented. Assuming R-parity conservation, selectrons and squarks of the Minimal Supersymmetric Standard Model are excluded for masses up to 65 GeV in a new region of the standard parameter space. Admitting in addition a R-parity violating Yukawa coupling $\lambd

A. Borowiec, M. Ferraris, M. Francaviglia, I. Volovich

It has been recently shown that, in the first order (Palatini) formalism, there is universality of Einstein equations and Komar energy-momentum complex, in the sense that for a generic nonlinear Lagrangian depending only on the scalar curvature of a metric and a torsionless connection one always gets Einstein equations and Komar's expression for the energy-m

Pei-Ming Ho, Yong-Shi Wu

We apply noncommutative geometry to a system of N parallel D-branes, which is interpreted as a quantum space. The Dirac operator defining the quantum differential calculus is identified to be the supercharge for strings connecting D-branes. As a result of the calculus, Connes' Yang-Mills action functional on the quantum space reproduces the dimensionally red

X. Gonze, Ph. Ghosez, R. W. Godby

We examine the density-functional theory of macroscopic insulators, obtained in the large-cluster limit or under periodic boundary conditions. For polar crystals, we find that the two procedures are not equivalent. In a large-cluster case, the exact exchange-correlation potential acquires a homogeneous ``electric field'' which is absent from the usual local

Arianna Montorsi, Vittorio Penna

We describe the quantum dynamics of the Hubbard model at semi-classical level, by implementing the Time-Dependent Variational Principle (TDVP) procedure on appropriate macroscopic wavefunctions constructed in terms of su(2)-coherent states. Within the TDVP procedure, such states turn out to include a time-dependent quantum phase, part of which can be recogni

Th. M. Nieuwenhuizen, C. N. A. van Duin

On the basis of a recent field theory for site-disordered spin glasses a Ginzburg-Landau free energy is proposed to describe the low temperatures glassy phase(s) of site-disordered magnets. The prefactors of the cubic and dominant quartic terms change gradually along the transition line in the concentration-temperature phase diagram. Either of them may vanis

Thomas Vojta

We investigate the sensitivity of the time evolution of a kinetic Ising model with Glauber dynamics against the initial conditions. To do so we apply the "damage spreading" method, i.e., we study the simultaneous evolution of two identical systems subjected to the same thermal noise. We derive a master equation for the joint probability distribution of the t