February 1998 arXiv papers — page 13

Bradley M. Peterson, Ignaz Wanders, Ray Bertram, James F. Hunley

We present the light curves obtained during an eight-year program of optical spectroscopic monitoring of nine Seyfert 1 galaxies: 3C 120, Akn 120, Mrk 79, Mrk 110, Mrk 335, Mrk 509, Mrk 590, Mrk 704, and Mrk 817. All objects show significant variability in both the continuum and emission-line fluxes. We use cross-correlation analysis to derive the sizes of t

Bradley M. Peterson, Ignaz Wanders, Keith Horne, Stefan Collier

We describe a model-independent method of assessing the uncertainties in cross-correlation lags determined from AGN light curves, and use this method to investigate the reality of lags between UV and optical continuum variations in well-studied AGNs. Our results confirm the existence of such lags in NGC 7469. We find that the continuum variations at 1825 A,

Armen Sedrakian, James M. Cordes

We discuss the spin evolution of pulsars in the case where a superfluid component of the star is coupled to the observable crust on long, spindown timescales. The momentum transfer from the superfluid interior results in an apparent decay of the external torque and, after a dramatic increase, to an asymptotic decrease of the generic value of the braking inde

J. Siebert, W. Brinkmann

We present ROSAT HRI observations of six quasars with redshifts >3.4: PKS 0335-122, S4 0620+389, B1422+231, PKS 2215+02, Q 2239-386 and PC 2331+0216. We include the observation of the radio-quiet quasar BG 57 9, whose redshift has recently been revised to z = 0.965. S4 0620+389, B1422+231, PKS 2215+02 and BG 57 9 are detected in the ROSAT energy band (0.1-2.

Michele Bellazzini

A detailed analysis of the Fundamental Plane properties of Globular Cluster is performed. If a sample of ordinary King-model clusters is considered, it is found that, in the "S-space" defined by the parameters (log r_c, log sigma_0, mu_V(0)), their configuration is similar to a straight line. It is shown that, with rather simple assumptions, a simult

T. R. Seshadri, K. Subramanian

Radiation which has a quadrupole component of anisotropy, can get polarized by Thomson scattering from charged particles. In the cosmological context, the microwave background photons develop significant quadrupole anisotropy as they free stream away from the the epoch of standard recombination. Reionization in the post recombination era can provide free ele

J. J. M. in 't Zand, J. Heise, J. M. Muller, A. Bazzano

We report the discovery of a fairly bright transient during observations with the Wide Field Cameras on board the BeppoSAX satellite in September 1996. It was detected at a peak intensity of 0.1 Crab (2 to 10 keV) and lasted between 6 and 40 days above a detection threshold of 2 mCrab. Two very bright type I X-ray bursts were detected from this transient in

Stefano Andreon

Two contradictory results on the evolution of SO galaxies now exist in the recent literature; either S0s are old ($z_{formation}>2$) and are evoloving passively or most of them formed at $z<0.5$, as implied by the deficit of S0s in intermediate redshift ($z\sim0.5$) clusters. The resolution of this controversy may be that the apparent deficit of S0s has been

M. J. Drinkwater, E. M. Sadler, J. I. Davies, R. J. Dickens

We are using the 2dF spectrograph on the Anglo-Australian Telescope to obtain spectra for a complete sample of all 14000 objects with 16.5<B<19.7 in a 12 square degree area centred on the Fornax cluster. The aims of this project include the study of dwarf galaxies in the cluster (both known low surface brightness objects and putative normal surface brightnes

Philippe Bagot, Simon F. Portegies Zwart, Lev R. Yungelson

The evolution of the comoving cosmic merger-rate density of neutron star binaries n_c(z) is calculated using a distribution of their merging times provided by population-synthesis computations of binary stars. We adopt an exponential law for the star formation rate with various timescales for different morphological types of galaxies. For elliptical galaxies

Mikhail Grinberg

Let g be a complex semisimple Lie algebra, and f : g --> g/G the adjoint quotient map. Springer theory of Weyl group representations can be seen as the study of the singularities of f. We give a generalization of Springer theory to visible, polar representations. It is a class of rational representations of complex reductive groups, for which the invariant t

Zhang Yang

The dependence of the fractal behaviors of the pomeron induced system in deep inelastic lepton-nucleon scattering upon the diffractive kinematic variables is found rather robust and not sensitive to the distinct parameterization of the pomeron flux factor and structure function. A feasible experimental test of the phenomenological pomeron-exchanged model bas

David Carpentier, Pierre Le Doussal

We present a novel RG approach to 2D random XY models using direct and replicated Coulomb gas methods. By including fusion of environments (charge fusion in the replicated CG) it follows the distribution of local disorder, found to obey a Kolmogorov non linear equation (KPP) with traveling wave solutions. At low T and weak disorder it yields a glassy XY phas

K. Yabana, G. F. Bertsch

The time-dependent local-density approximation (TDLDA) is shown to remain accurate in describing the atomic response of IB elements under the additional approximation of using pseudopotentials to treat the effects of core electrons. This extends the work of Zangwill and Soven who showed the utility of the all-electron TDLDA in the atomic response problem.

C. A. Ogilvie

Particle production and correlation functions from Au+Au reactions have been measured as a function of both beam energy (2-10.7AGeV) and impact parameter. These results are used to probe the dynamics of heavy-ion reactions, confront hadronic models over a wide range of conditions and to search for the onset of new phenomena.

David M. Riley, Mark C. Wilson

Let K be a field of positive characteristic p, let R be either a group algebra K[G] or a restricted enveloping algebra u(L), and let I be the augmentation ideal of R. We first characterize those R for which I satisfies a polynomial identity not satisfied by the algebra of all 2-by-2 matrices over K. Then we examine those R for which I satisfies a semigroup i

Adriano Di Giacomo, Manu Mathur

It is shown that SU(N) gauge theory coupled to adjoint Higgs can be explicitly re-written in terms of SU(N) gauge invariant dynamical variables with local physical interactions. The resultant theory has a novel compact abelian $U(1)^{(N - 1)}$ gauge invariance. The above abelian gauge invariance is related to the adjoint Higgs field and not to the gauge grou

Vladimir S. Mashkevich

This paper is a sequel to the series of papers [gr-qc/9409010, gr-qc/9505034, gr-qc/9603022, gr-qc/9609035, gr-qc/9609046, gr-qc/9704033, gr-qc/9704038, gr-qc/9708014], being an immediate continuation and supplement to the last of them, where gravitational autolocalization of a body has been considered. A resulting solution, which describes a one-place locat

Raymond E. Goldstein, Thomas R. Powers, Chris H. Wiggins

Exploiting the &#34;natural&#34; frame of space curves, we formulate an intrinsic dynamics of twisted elastic filaments in viscous fluids. A pair of coupled nonlinear equations describing the temporal evolution of the filament&#39;s complex curvature and twist density embodies the dynamic interplay of twist and writhe. These are used to illustrate a novel no

L. N. Shchur, S. S. Kosyakov

The probability of simultaneous occurence of at least k spanning clusters has been studied by Monte Carlo simulations on the 2D square lattice at the bond percolation threshold Pc=1/2. The calculated probabilities for free boundary conditions and periodic boundary conditions are in a very good coincidence with the exact formulae developed recently by Cardy.

M. C. de Andrade, R. Chau, R. P. Dickey, N. R. Dilley

The non-Fermi-liquid (NFL) behavior observed in the low temperature specific heat $C(T)$ and magnetic susceptibility $χ(T)$ of f-electron systems is analyzed within the context of a recently developed theory based on Griffiths singularities. Measurements of $C(T)$ and $χ(T)$ in the systems $Th_{1-x}U_{x}Pd_{2}Al_{3}$, $Y_{1-x}U_{x}Pd_3$, and $UCu_{5-x}M_{x}$

K. Z. Stanek

We live in a dusty Universe, and correcting for the dust extinction and reddening affects almost all aspects of the optical astronomy. Recently Schlegel, Finkbeiner & Davis published an all-sky reddening map based on the COBE/DIRBE and IRAS/ISSA infrared sky surveys. Their map is intended to supersede the older Burstein & Heiles reddening estimates. In this

S. P. Driver, A. Fernandez-Soto, W. J. Couch, S. C. Odewahn

We combine the photometric redshift data of Fernandez-Soto et al. (1997) with the morphological data of Odewahn et al. (1996) for all galaxies with I < 26.0 detected in the Hubble Deep Field. From this combined catalog we generate the morphological galaxy number-counts and corresponding redshift distributions and compare these to the predictions of high norm

Brad K. Gibson

Recent determinations of the upper mass limit to the local initial mass function (IMF) claim a value of m(upper)=50+/-10 solar masses, based upon direct comparisons of the observed oxygen and iron abundances in metal-poor stars with the predicted stellar yields from Type II supernovae (SNe). An unappreciated uncertainty in these analyses is the input physics

Murat Gunaydin, Djordje Minic

We identify the two dimensional AdS subsupergroup $OSp(16/2,R)$ of the M-theory supergroup $OSp(1/32,R)$ which captures the dynamics of $n$ $D0$-branes in the large $n$ limit of Matrix theory. The $Sp(2,R)$ factor in the even subgroup $SO(16) \times Sp(2,R)$ of $OSp(16/2,R)$ corresponds to the AdS extension of the Poincare symmetry of the longitudinal direct

J. H. Kühn, G. Rodrigo

A sizeable difference in the differential production cross section of top and antitop quarks, respectively, is predicted for hadronically produced heavy quarks. It is of order $\alpha_s$ and arises from the interference between charge odd and even amplitudes respectively. For the TEVATRON it amounts to approximately 5-10% in the region where the cross sectio

Shoichi Ichinose, Sergei D. Odintsov

The conformal anomaly for 4D gravity-matter theories, which are non-minimally coupled with the dilaton, is systematically studied. Special care is taken for: rescaling of fields, treatment of total derivatives, hermiticity of the system operator and choice of measure. Scalar, spinor and vector fields are taken as the matter quantum fields and their explicit

Nissan Itzhaki, Juan M. Maldacena, Jacob Sonnenschein, Shimon Yankielowicz

We consider field theories with sixteen supersymmetries, which includes U(N) Yang-Mills theories in various dimensions, and argue that their large N limit is related to certain supergravity solutions. We study this by considering a system of D-branes in string theory and then taking a limit where the brane worldvolume theory decouples from gravity. At the sa

E. A. Kolganova, A. K. Motovilov, S. A. Sofianos

We present a new, mathematically rigorous, method suitable for bound state and scattering processes calculations for various three atomic or molecular systems where the underlying forces are of a hard-core nature. We employed this method to calculate the binding energies and the ultra-low energy scattering phase shifts below as well as above the break-up thr

G. H. Rawitscher

A wave-function framework for the theory of the (e,e&#39;N) reaction is presented in order to justify the use of coupled channel equations in the usual Feynman matrix element. The overall wave function containing the electron and nucleon coordinates is expanded in a basis set of eigenstates of the nuclear Hamiltonian, which contain both bound states as well

G. H. Rawitscher, I. Koltracht, R. A. Gonzales

A new spectral type method for solving the one dimensional quantum-mechanical Lippmann-Schwinger integral equation in configuration space is described. The radial interval is divided into partitions, not necessarily of equal length. Two independent local solutions of the integral equation are obtained in each interval via Clenshaw-Curtis quadrature in terms

Mikhail Kapranov

We develop an approach to noncommutative algebraic geometry ``in the perturbative regime&#34; around ordinary commutative geometry. Let R be a noncommutative algebra and A=R/[R,R] its commutativization. We describe what should be the formal neighborhood of M=Spec(A) in the (nonexistent) space Spec(R). This is a ringed space (M,O) where O is a certain sheaf o

Pietro Fre&#39;

In this talk I review both accomplished results and work in progress on the use of solvable Lie algebras as an intrinsic algebraic characterization of the scalar field sector of M--theory low energy effective lagrangians. In particular I review the application of these techniques in obtaining the most general form of BPS black hole solutions.

Tatsuo Kobayashi, Jisuke Kubo, George Zoupanos

It is proven that the recently found, renormalization-group invariant sum rule for the soft scalar masses in softly-broken N=1 supersymmetric gauge-Yukawa unified theories can be extended to all orders in perturbation theory. In the case of finite unified theories, the sum rule ensures the all-loop finiteness in the soft supersymmetry breaking sector. As a b

Peter Hasenfratz

The classically perfect action of QCD requires no tuning to get the pion massless in the broken phase: the critical bare mass $m_q^c$ is zero. Neither the vector nor the flavour non-singlet axial vector currents need renormalization. Further, there is no mixing between four-fermion operators in different chiral representations. The order parameter of chiral

QCDTARO Collaboration

We present our new results on the renormalization group coupling flow obtained i n 3 dimensional coupling space $(β_{11},β_{12},β_{twist})$. The value of $β_{twist}$ turns out to be small and the coupling flow projected on $(β_{11},β_{12})$ plane is very similar with the previous result obtained in the 2 dimensional coupling space.

T. K. Ng, Chi-Ho Cheng

A supersymmetric way of imposing the constraint of no double occupancy in models with strong on-site Coulomb repulsion is presented in this paper. In this formulation the physical operators in the constrainted Hilbert space are invariant under local unitary transformations mixing boson and fermion representations. As an illustration the formulation is applie

R. Kallenbach, F. M. Ipavich, P. Bochsler, S. Hefti

We present first results on the Ca isotopic abundances derived from the high resolution Mass Time-of-Flight (MTOF) spectrometer of the charge, element, and isotope analysis system (CELIAS) experiment on board the Solar and Heliospheric Observatory (SOHO). We obtain isotopic ratios 40Ca/42Ca = (128+-47) and 40Ca/44Ca = (50+-8), consistent with terrestrial val

Frederick K. Lamb, M. Coleman Miller, Dimitrios Psaltis

The dramatic discovery with the Rossi X-Ray Timing Explorer satellite of remarkably coherent $\sim$300--1200 Hz oscillations in the X-ray brightness of some sixteen neutron stars in low-mass binary systems has spurred theoretical modeling of these oscillations and investigation of their implications for the neutron stars and accretion flows in these systems.

Stephen Holland

The distance to the centroid of the M31 globular cluster system is determined by fitting theoretical isochrones to the observed red-giant branches of fourteen globular clusters in M31. The mean true distance modulus of the M31 globular clusters is found to be 24.47 +/- 0.07 mag. This is consistent with distance modulii for M31 that have been obtained using o

V. Urpin, U. Geppert, D. Konenkov

The evolution of neutron stars in close binary systems with a low-mass companion is considered assuming the magnetic field to be confined within the solid crust. We adopt the standard scenario of the evolution in a close binary system in accordance with which the neutron star passes throughout four evolutionary phases (&#34;isolated pulsar&#34; -- &#34;prope

S. J. Unger, P. Roche, I. Negueruela, F. A. Ringwald

V635 Cas is the optical counterpart of the X-ray binary system 4U 0115+63. It was previously tentatively identified as a Be star based on its optical colours and the presence of H alpha emission. Our observations indicate that it is an O9e star. This is the first direct determination of this star&#39;s optical spectral type. The presence of a hotter companio

Soma Mukherjee, Eric D. Feigelson, Gutti Jogesh Babu, Fionn Murtagh

A multivariate analysis of gamma-ray burst (GRB) bulk properties is presented to discriminate between distinct classes of GRBs. Several variables representing burst duration, fluence and spectral hardness are considered. Two multivariate clustering procedures are used on a sample of 797 bursts from the Third BATSE Catalog: a nonparametric average linkage hie

Yu. A. Fadeyev, D. Gillet

The structure of steady plane-parallel radiative shock waves propagating through the hydrogen gas undergoing partial ionization and excitation of bound atomic states is investigated in terms of the self-consistent solution of the equations of fluid dynamics, radiation transfer and atomic kinetics. The shock wave model is represented by a flat finite slab wit

Hans A. Bethe, G. E. Brown

Beginning from massive binaries in the Galaxy we evolve black-hole, neutron-star binaries and binary neutron stars, such as the Hulse-Taylor system PSR 1913+16. The new point in our evolution is a quantitative calculation of the accretion of matter by a neutron star in common envelope evolution which sends it into a black hole. We calculate the mass of the l

Boudewijn F. Roukema, Vincent Blanloeil

The space-like hypersurface of the Universe at the present cosmological time is a three-dimensional manifold. A non-trivial global topology of this space-like hypersurface would imply that the apparently observable universe (the sphere of particle horizon radius) could contain several images of the single, physical Universe. Recent three-dimensional techniqu

F. S. Nogueira, M. B. Silva Neto, N. F. Svaiter

We analyze the finite temperature chiral restoration transition of the $(D=d+1)$-dimensional Gross-Neveu model for the case of a large number of flavors and fixed total fermion number. This leads to the study of the model with a nonzero imaginary chemical potential. In this formulation of the theory, we have obtained that, in the transition region, the model

Paul B. Slater

We derive explicit expressions for the volume elements of both the minimal and maximal monotone metrics over the (n^{2} - 1)-dimensional convex set of n x n density matrices for the cases n = 3 and 4. We make further progress for the specific n = 3 maximal-monotone case, by taking the limit of a certain ratio of integration results, obtained using an orthogo

L. Burlachkov, D. Giller, R. Prozorov

Numerical studies of the flux creep in superconductors show that the distribution of the magnetic field at any stage of the creep process can be well described by the condition of spatial constancy of the activation energy $U$ independently on the particular dependence of $U$ on the field B and current $j$. This results from a self-organization of the creep

C. Panagiotakopoulos

We present a supergravity inflationary scenario in which the inflaton field takes values considerably larger than the Planck scale. It is based on a class of inflationary potentials which can be derived from ``singular&#39;&#39; Kaehler potentials assuming simple superpotentials of the type $W\simS^n$. To this class belong, among many others, all potentials

R. Aloisio, V. Azcoiti, G. Di Carlo, A. Galante

We report results of simulations of strong coupling, finite density QCD obtained within a MFA inspired approach where the fermion determinant in the integration measure is replaced by its absolute value. Contrary to the standard wisdom, we show that within this approach a clear signal of a phase transition appears with a critical chemical potential in extrem

Owen Dando, Ruth Gregory

We examine the field equations of a self-gravitating global string in low energy superstring gravity, allowing for an arbitrary coupling of the global string to the dilaton. Massive and massless dilatons are considered. For the massive dilaton the spacetime is similar to the recently discovered non-singular time-dependent Einstein self-gravitating global str

A. Sibirtsev, W. Cassing

The cross sections of the reaction $pp \to N K Y$ for $K^+$ or $K^0$ mesons and $Λ$ or $Σ$ hyperons are calculated within the boson exchange model including pion and kaon exchange diagrams. We analyze the dependence of the results on the accuracy of the input $πN$ amplitude. By fixing the $πNN $ coupling constant and the cut-off parameter $Λ_π$ at the $πNN$

B. R. Martin, G. C. Oades

The amplitudes at a series of discrete energies obtained from a previuos analysis of pbar+p -> pi+pi have been used as input to a global energy- dependent analysis of data in the momentum range 360 - 1550 MeV/c. The results confirm the previous analysis and yield refined values for meson resonance parameters in this energy region.

Kay Joerg Wiese

We present a simple argument to show that the beta-function of the d-dimensional KPZ-equation (d>=2) is to all orders in perturbation theory given by beta(g) = (d-2) g - 2/(8 pi)^(d/2) Gamma(2-d/2) g^2 . Neither the dynamical exponent z nor the roughness-exponent zeta have any correction in any order of perturbation theory. This shows that standard perturbat

Roy Maartens, Josep Triginer

Using a simple thermo-hydrodynamic model that respects relativistic causality, we revisit the analysis of qualitative features of acoustic oscillations in the photon-baryon fluid. The growing photon mean free path introduces transient effects that can be modelled by the causal generalization of relativistic Navier-Stokes-Fourier theory. Causal thermodynamics

Angel Ballesteros, Orlando Ragnisco

A universal algorithm to construct N-particle (classical and quantum) completely integrable Hamiltonian systems from representations of coalgebras with Casimir element is presented. In particular, this construction shows that quantum deformations can be interpreted as generating structures for integrable deformations of Hamiltonian systems with coalgebra sym

D. Bazeia

We investigate generalizations of the Burgers and Burgers-Huxley equations. The investigations we offer focus attention mainly on presenting explict analytical solutions by means of relating these generalized equations to relativistic 1+1 dimensional systems of scalar fields where topological solutions are known to play a role. Emphasis is given on chiral so

G. N. Nugmanova

The Lakshmanan equivalent counterparts of the some Myrzakulov equations are found.

D. G. Cory, W. Mass, M. Price, E. Knill

Quantum error correction is required to compensate for the fragility of the state of a quantum computer. We report the first experimental implementations of quantum error correction and confirm the expected state stabilization. In NMR computing, however, a net improvement in the signal-to-noise would require very high polarization. The experiment implemented

R. F. Salzgeber, V. Mandelshtam, Ch. Schlier, H. S. Taylor

We calculated all 2967 even and odd bound states of the adiabatic ground state of NO_2, using a modification of the ab initio potential energy surface of Leonardi et al. [J. Chem. Phys. 105, 9051 (1996)]. The calculation was performed by harmonic inversion of the Chebyshev correlation function generated by a DVR Hamiltonian in Radau coordinates. The relative

C. W. Johnson, G. F. Bertsch, W. D. Hazelton

An iterative algorithm is presented for solving the RPA equations of linear response. The method optimally computes the energy-weighted moments of the strength function, allowing one to match the computational effort to the intrinsic accuracy of the basic mean-field approximation, avoiding the problem of solving very large matrices. For local interactions, t

P. Bozek, Y. B. He, J. Hufner

The space-time development of a quark-gluon plasma is calculated from a Vlasov equation for the distribution function of quasiparticles with medium dependent masses. At each space-time point the masses are calculated selfconsistently from a gap equation, whose form is determined by the requirement that in thermal equilibrium and for a range of temperatures t

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

In the theory of deep inelastic scattering (DIS) the final state interaction (FSI) between the struck quark and the remnants of the target is usually assumed to be negligible in the Bjorken limit. This assumption, still awaiting a full validation within nonperturbative QCD, is investigated in a model composed by two relativistic particles, interacting via a

E. G. Nikonov, A. A. Shanenko, V. D. Toneev

Particularities of the statistical mixed phase model for describing the deconfinement phase transition and physics constraints on the model parameters, are discussed. The modifications proposed concern an improved treatment of hadron-hadron interactions within the nonlinear mean-field model of nuclear matter and an inclusion of the one-gluon exchange correct

R. Schicker, M. Axiotis, H. Tsertos

A novel approach for a versatile first level dielectron trigger is presented. This trigger operates in the low multiplicity environment of nucleon-nucleon reactions as well as in the high multiplicity situation of nucleus-nucleus collisions. For optimal trigger performance, time of flight conditions for the two fastest particles of the event are combined wit

F. Hibou, O. Bing, M. Boivin, P. Courtat

The total cross section of the pp -> pp eta&#39; reaction has been measured at two energies near threshold by detecting the final protons in a magnetic spectrometer. The values obtained are about a factor of 70 less than for the corresponding eta production, in good agreement with the predictions of a one-pion-exchange model.

Bruce W. Jordan, Ron Livné

Poonen and Stoll have shown that the reduced Shafarevich-Tate group of a principally polarized abelian variety over a global field can have order twice a square (the odd case) as well as a square (the even case). For a curve over a global field, they give a local diophantine criterion for its jacobian to be even or odd. In this note we use the Cherednik-Drin

Greg Kuperberg, Krystyna Kuperberg

Using the theory of plugs and the self-insertion construction due to the second author, we prove that a foliation of any codimension of any manifold can be modified in a real analytic or piecewise-linear fashion so that all minimal sets have codimension 1. In particular, the 3-sphere S^3 has a real analytic dynamical system such that all limit sets are 2-dim

David M. Riley, Mark C. Wilson

Denote by (R,.) the multiplicative semigroup of an associative algebra R over an infinite field, and let (R,*) represent R when viewed as a semigroup via the circle operation x*y=x+y+xy. In this paper we characterize the existence of an identity in these semigroups in terms of the Lie structure of R. Namely, we prove that the following conditions on R are eq

Arthur G. Sergheyev

For the class of systems of PDEs, for which infinitesimal translations (with respect to some (in)dependent variables) possess specific finite-dimensional invariant subspaces of the space of generalized symmetries of the system considered. We establish when there exist generalized symmetries from these subspaces, which depend from the above-mentioned variable

Erik N. Tjotta

We describe the Hilbert scheme components parametrizing lines and conics on the space of determinantal nets of conics, N. As an application, we use the quantum Lefschetz hyperplane principle to compute the instanton numbers of rational curves on a complete intersection Calabi-Yau threefold in N. We also compute the number of lines and conics on some Calabi-Y

A. A. Balinsky, W. D. Evans

A virial theorem is established for the operator proposed by Brown and Ravenhall as a model for relativistic one-electron atoms. As a consequence, it is proved that the operator has no eigenvalues greater than $\max(m c^2, 2 αZ - \frac{1}{2})$, where $α$ is the fine structure constant, for all values of the nuclear charge $Z$ below the critical value $Z_c$:

Byung-Jay Kahng

As a generalization of the linear Poisson bracket on the dual space of a Lie algebra, we introduce certain non-linear Poisson brackets which are ``cocycle perturbations&#39;&#39; of the linear Poisson bracket. We show that these special Poisson brackets are equivalent to Poisson brackets of central extension type, which resemble the central extensions of an

Thomas Friedrich

The aim of this paper is the construction of spinor bundles of Cartan type over certain non-orientable manifolds.

Andre Lukas, Burt A. Ovrut, Daniel Waldram

We review cosmological solutions of type II superstrings and M-theory, emphasizing the role of non-vanishing Ramond form backgrounds. Compactifications on flat and, more generally, maximally symmetric spatial subspaces are presented. We give a physical discussion of both inflating and subluminally expanding cosmological solutions of such theories and explore

Tim R. Morris

These two lectures cover some of the advances that underpin recent progress in deriving continuum solutions from the exact renormalization group. We concentrate on concepts and on exact non-perturbative statements, but in the process will describe how real non-perturbative calculations can be done, particularly within derivative expansion approximations. An

Giovanni Salesi, Erasmo Recami

The Barut--Zanghi (BZ) theory can be regarded as the most satisfactory picture of a classical spinning electron and constitutes a natural &#34;classical limit&#34; of the Dirac equation. The BZ model has been analytically studied in some previous papers of ours in the case of free particles. By contrast, in this letter we consider the case of external fields

C. Heineman, C. Martin, D. Vautherin, E. Iancu

Variational calculations using Gaussian wave functionals combined with an approximate projection on gauge invariant states are presented. We find that the energy exhibits a minimum for a wave functional centered around a non vanishing background magnetic field. We show that divergences can be removed by a renormalization of the coupling constant. The resulti

Dirk Schlingemann

In order to construct examples for interacting quantum field theory models, the methods of euclidean field theory turned out to be powerful tools since they make use of the techniques of classical statistical mechanics. Starting from an appropriate set of euclidean n-point functions (Schwinger distributions), a Wightman theory can be reconstructed by an appl

Wojciech Wislicki

An idea of possible anomalous contribution of non-perturbative origin to the nucleon spin was examined by analysing data on spin asymmetries in polarized deep inelastic scattering of leptons on nucleons. The region of high Bjorken x was explored. It was shown that experimental data available at present do not evidence for this effect.

M. S. Berger

We analyze the prospects at a muon collider for measuring chargino masses in the $μ^+μ^-\to \tildeχ^+\tildeχ^-$ processes in the threshold region. We find that a measurement of the lightest chargino mass to better than 200 MeV is possible with 100~fb$^{-1}$ luminosity. The muon sneutrino mass can also be simultaneously measured to a few GeV.

Z. Bern, L. Dixon, D. A. Kosower, A. Signer

We review recent developments in the calculation of QCD loop amplitudes with several external legs, and their application to next-to-leading order jet production cross-sections. When a number of calculational tools are combined together --- helicity, color and supersymmetry decompositions, plus unitarity and factorization properties --- it becomes possible t

J. Fleischer, M. Yu. Kalmykov, O. L. Veretin

The method of the large mass expansion (LME) has the technical advantage that two-loop integrals occur only as bubbles with large masses. In many cases only one large mass occurs. In such cases these integrals are expressible in terms of $Γ$-functions, i.e. they can be handled completely analytically avoiding even recursions and therefore this approach may f

Hidenaga Yamagishi, Ismail Zahed

In the absence of nucleons, we use partial wave unitarity, to show that the chiral expansion parameter must be close to $p^2/4πf_π^2$ rather than $p^2/16π^2 f_π^2$ as previously suggested, where $p$ is a typical pion momentum and $f_π$ the pion decay constant. When nucleons are included, we apply the Tani-Foldy-Wouthuysen (TFW) transformation to the pion-nuc

Bogdan A. Dobrescu

An interesting class of models of dynamical electroweak symmetry breaking allows only the third generation fermions to acquire dynamical masses, such that the masses of the first two generations should be given by coupling to a nonstandard ``Higgs&#39;&#39; doublet. The scalars in this case have large couplings to the second generation, so that they are copi

Gunnar S. Bali, Christoph Schlichter, Klaus Schilling

Various field strength correlators are investigated in the maximal Abelian projection of pure SU(2) lattice gauge theory. High precision measurements of the colour fields, monopole currents, their curls and divergences allow for detailed checks of the dual superconductor scenario. On this basis, we perform a Ginzburg-Landau type analysis of the flux tube pro

Stephan Lammel

These lectures contain an introduction to the search for supersymmetry at hadron colliders. The Tevatron is one of high-energy physics most sophisticated tools. The high center-of-mass energy of its proton-antiproton collisions makes it an ideal place to search for physics beyond the Standard Model, such as supersymmetry. Two experiments, CDF and DØ, complet

M. Woods

An electron beam polarization of 80% or greater will be a key feature of a 1 TeV Linear Collider. Accurate measurements of the beam polarization will therefore be needed. We discuss design considerations and capabilities for a Compton-scattering polarimeter located in the extraction line from the Interaction Point. Polarization measurements with 1% accuracy

Roy Maartens, William Lesame, George Ellis

In an irrotational dust universe, the locally free gravitational field is covariantly described by the gravito-electric and gravito-magnetic tensors $E_{ab}$ and $H_{ab}$. In Newtonian theory, $H_{ab}=0$ and $E_{ab}$ is the tidal tensor. Newtonian-like dust universes in general relativity (i.e. with $H_{ab}=0$, often called `silent&#39;) have been shown to b

R. S. Markiewicz, C. Kusko

Recent tunneling observations of a pseudogap in Bi_2Sr_2CaCu_2O_{8+delta} are not necessarily evidence that the pseudogap is associated with superconducting fluctuations. The data are here analyzed as a competition between superconductivity and a density wave (taken as a simplified model for a striped phase).

R. S. Markiewicz, M. T. Vaughn

The various nesting and pairing instabilities of the generalized Van Hove scenario can be classified via an SO(8) spectrum-generating algebra. An SO(6) subgroup is an approximate symmetry group of the model, having two 6-dimensional representations (`superspins&#39;). This group contains as subgroups both the SO(5) and SO(4) groups found by Zhang, while one

D. Bolle, R. Erichsen

Perceptrons with graded input-output relations and a limited output precision are studied within the Gardner-Derrida canonical ensemble approach. Soft non- negative error measures are introduced allowing for extended retrieval properties. In particular, the performance of these systems for a linear and quadratic error measure, corresponding to the perceptron

R. O. Kuzian, R. Hayn, A. F. Barabanov, L. A. Maksimov

A self-consistent, spin rotational invariant Green&#39;s function procedure has been developed to calculate the spectral function of carrier excitations in the spin-fermion model for the CuO2 plane. We start from the mean field description of a spin polaron in the Mori-Zwanzig projection method. In order to determine the spin polaron lifetime in the self-con

I. Vakarchuk, V. Tkachuk, T. Kuliy

The dilute Heisenberg ferromagnet is studied taking into account fluctuations of magnetization caused by disorder. A self-consistent system of equations for magnetization and its mean quadratic fluctuations is derived within the configurationally averaged two-time temperature Green&#39;s function method. This system of equations is analised at low concentrat

Haranath Ghosh, Manidipa Mitra, S. N. Behera, S. K. Ghatak

The co-existence of band Jahn-Teller (BJT) effect with superconductivity (SC) is studied for correlated systems, with orbitally degenerate bands using a simple model. The Hubbard model for a doubly degenerate orbital with the on-site intraorbital Coulomb repulsion treated in the slave boson formalism and the interorbital Coulomb repulsion treated in the Hart

M. A. Smondyrev, A. A. Shanenko, J. T. Devreese

A criterion, proposed by the present authors, is used to derive numerical results for the stability of a large bipolaron embedded in a polaron gas. The main conclusion is that an isolated metastable bipolaron can be stabilized by the polaron gas surroundings because of the Fermi statistics of polarons. On the other hand, it is found that the exchange interac

A. M. Povolotsky, V. B. Priezzhev, R. R. Shcherbakov

We investigate the dynamics of Eulerian walkers as a model of self-organized criticality. The evolution of the system is subdivided into characteristic periods which can be seen as avalanches. The structure of avalanches is described and the critical exponent in the distribution of first avalanches $τ=2$ is determined. We also study a mean square displacemen

P. De Los Rios, M. Marsili, M. Vendruscolo

We report on extensive numerical simulations on the Bak-Sneppen model in high dimensions. We uncover a very rich behavior as a function of dimensionality. For d>2 the avalanche cluster becomes fractal and for d \ge 4 the process becomes transient. Finally the exponents reach their mean field values for d=d_c=8, which is then the upper critical dimension of t

Jun&#39;ichi Shiraishi, Mahito Kohmoto, Kazumi Maki

We study the vortex state in a magnetic field parallel to the $c$ axis in the framework of the extended Ginzburg Landau equation. We find the vortex acquires a fourfold modulation proportional to $\cos(4ϕ)$ where $ϕ$ is the angle ${\bf r}$ makes with the $a$-axis. This term gives rise to an attractive interaction between two vortices when they are aligned pa