May 1997 arXiv papers — page 10

U. Frisch, D. Sornette

Stretched exponential probability density functions (pdf), having the form of the exponential of minus a fractional power of the argument, are commonly found in turbulence and other areas. They can arise because of an underlying random multiplicative process. For this, a theory of extreme deviations is developed, devoted to the far tail of the pdf of the sum

Wei-Shu Hou, B. Tseng

The experimental hint of large $B\to η^\prime + X_s$ is linked to the $b\to s$ penguins via the gluon anomaly. Using running $α_s$ in the $η^\prime$-$g$-$g$ coupling, the standard $b\to sg^*$ penguin alone seems insufficient, calling for the need of dipole $b\to sg$ at 10% level from new physics, which could also resolve the ${\cal B}_{s.l.}$ and charm count

Petre Dita, Nicolae Grama

We show that with a few modifications the Adomian's method for solving second order differential equations can be used to obtain the known results of the special functions of mathematical physics. The modifications are necessary in order to take correctly into account the behaviour of the solutions in the neighborhood of the singular points.

Yuri Shtanov

We account for the origin of the laws of quantum probabilities in the de Broglie-Bohm (pilot wave) formulation of quantum theory by considering the property of ergodicity likely to characterise the dynamics of microscopic quantum systems.

Denis Uglov

The decompositions of the Fock and Basic modules of the affine Lie algebra \hat{sl(N)} into irreducible submodules of the Yangian algebra Y(gl(N)) are constructed. Each of the irreducible submodules admits the unique up to normalization eigenbasis of the maximal commutative subalgebra of the Yangian. The elements of this eigenbasis are identified with specia

R. M. Santilli

We recall that the Minkowskian geometry possesses basic units of space and time which are invariant under the Poincaré symmetry. We then show that, by comparison, the Riemannian geometry possesses space-time units which are not invariant under the symmetries of the Riemannian line element, thus causing evident physical ambiguities. We therefore introduce a n

R. M. Santilli

We submit a classical unification of the special and general relativities via the new isominkowskian geometry in which the two relativities are differentiated by the basic unit. We then show that the unification admits an operator image in which gravitation verifies the abstract axioms of relativistic quantum mechanics under a universal symmetry which is iso

Sergei G. Matinyan, Berndt Mueller, Dirk H. Rischke

We explore the correspondence between classical gluon radiation and quantum radiation in a coherent state for gluons produced in ultrarelativistic nuclear collisions. The expectation value of the invariant momentum distribution of gluons in the coherent state is found to agree with the gluon number distribution obtained classically from the solution of the Y

Oleg Belegradek, Ya'acov Peterzil, Frank Wagner

The authors investigate the structure of quasi-o-minimal groups. Among other results, they show that quasi-o-minimal groups are abelian, that quasi-o-minimal densely ordered archimedian groups are divisible, and that every divisible quasi-o-minimal group is o-miminal.

Changhyun Ahn, Radu Tatar

We study N=1 dualities in four dimensional supersymmetric gauge theories by D 6-branes wrapping around 3-cycles of Calabi-Yau threefolds in the type IIA string theory. We consider the models involving $SU(N_{c1})\times SU(N_{c2})$ product gauge group without or with adjoint matter in terms of geometrical realisation of the configuration of D 6-branes wrapped

S. G. Rajeev, O. T. Turgut

In this article, we will discuss geometric quantization of 2d QCD with fermionic and bosonic matter fields. We identify the respective large-N_c phase spaces as the infinite dimensional Grassmannian and the infinite dimensional Disc. The Hamiltonians are quadratic functions, and the resulting equations of motion for these classical systems are nonlinear. In

G. Grignani, L. Paniak, G. W. Semenoff, P. Sodano

Explicit computations of the partition function and correlation functions of Wilson and Polyakov loop operators in theta-sectors of two dimensional Yang-Mills theory on the line cylinder and torus are presented. Several observations about the correspondence of two dimensional Yang-Mills theory with unitary matrix quantum mechanics are presented. The incorpor

M. Bordag, G. T. Gillies, V. M. Mostepanenko

We calculate the constraints on the constants of hypothetical long-range interactions which follow from the recent measurement of the Casimir force. A comparison with previous constraints is given. The new constraints are up to a factor of 3000 stronger in some parameter regions .

Wladyslaw Marcinek

A simple algebraic model for charged particle moving in two dimensional space under influence of singular magnetic field is given. The fundamental assumption for the model is that every charged particle coupled to the magnetic field is transformed into a system of quasiparticles. It is also assumed for simplicity that there is in average N fluxes per particl

M. Maule, S. Sciuto

We show that the low-lying excitations of the one-dimensional Bose gas are described, at all orders in a 1/N expansion and at the first order in the inverse of the coupling constant, by an effective hamiltonian written in terms of an extended conformal algebra, namely the Cartan subalgebra of the $W_{1+\infty}\times \bar{W}_{1+\infty}$ algebra. This enables

Christian Wieczerkowski

We study the invariant unstable manifold of the trivial renormalization group fixed point tangent to the $ϕ^{4}$-vertex in three dimensions. We parametrize it by a running $ϕ^{4}$-coupling with linear step $β$-function. It is shown to have a renormalized double expansion in the running coupling and its logarithm.

Tomas Ortin

We give a brief overview of black-hole solutions in four-dimensional supergravity theories and their extremal and supersymmetric limits. We also address problems like cosmic censorship and no-hair theorems in supergravity theories. While supergravity by itself seems not to be enough to enforce cosmic censorship and absence of primary scalar hair, superstring

Enrique Alvarez, Patrick Meessen, Tomas Ortin

We study the transformation under the String Theory duality group of the observable charges (mass, angular momentum, NUT charge, electric, magnetic and different scalar charges) of four dimensional point-like objects whose asymptotic behavior constitutes a subclass closed under duality. The charges fall into two complex four-dimensional representations of th

David Kastor, K. Z. Win

Non-extreme black hole solutions of four dimensional, N=2 supergravity theories with Calabi-Yau prepotentials are presented, which generalize certain known double-extreme and extreme solutions. The boost parameters characterizing the nonextreme solutions must satisfy certain constraints, which effectively limit the functional independence of the moduli scala

R. Akhoury, V. I. Zakharov

We argue that the appearance of the Landau pole in the running coupling of QCD introduces 1/Q^2 power corrections in current correlation functions. These terms are not accounted for by the standard operator product expansion and is the price to be paid for the lack of a unique definition of the running coupling at the 1/Q^2 level. We review also possible phe

Xiangdong Ji

A class of purely-nonperturbative (PNP) composite operators is defined in Quantum Chromodynamics, which is perturbative scheme and scale independent and are useful to describe the internal structure of a strong interacting system. The operator product expansion in terms of the new operators cleanly separates the perturbative and nonperturbative physics witho

Robert D. Pisarski, Michel Tytgat

In vacuum, in the chiral limit the coupling of a pion to two on-shell photons is directly related to the coefficient of the axial anomaly in QED. This relationship is lost at any nonzero temperature. Explicit calculations show that the coupling decreases with temperature and vanishes at Tc, the temperature of chiral symmetry restoration.

B. de Carlos, J. R. Espinosa

In supersymmetric models whose gauge group includes an additional U(1) factor at the TeV scale, broken by the VEV of an standard model singlet S, the parameter space can accommodate a very light neutralino not ruled out experimentally. This higgsino-like fermion, stable if R-parity is conserved, can make a good cold dark matter candidate. We examine the ther

C. J. Maxwell, D. G. Tonge

We show that QCD Minkowski observables such as the $e^{+}e^{-}$ R-ratio and the hadronic tau decay $R_τ$ are completely determined by the effective charge (EC) beta-function, $ρ(x)$, corresponding to the Euclidean QCD vacuum polarization Adler D-function, together with the next-to-leading order (NLO) perturbative coefficient of D. An efficient numerical algo

V. R. Zoller

We study coherent enhancement of neutrino electro-magnetic conversion in crystals. Large coherency length which grows with the neutrino energy makes the coherent enhancement particularly effective for very small masses. We derive constraints on the conversion rate which follow from the Fresnel effects in scattering of neutrinos on atomic chains. We comment o

D. Bodeker, M. Laine, O. Philipsen

We study non-perturbative real time correlation functions at finite temperature. In order to see whether the classical term gives a good approximation in the high temperature limit T >> \hbarω, we consider the first \hbar^2 quantum corrections. We find that for the simplest non-trivial case, the quantum mechanical anharmonic oscillator, the classical result

A. Edin, G. Ingelman, J. Rathsman

The direct charmonium and bottomonium production rate observed at high-pt in pp-bar collisions at the Tevatron is factors of ten larger than predictions based on conventional perturbative QCD. We show that this excess can be accounted for by our model for soft colour interactions, previously introduced to describe in a novel way the large rapidity gap events

T. Yamanishi, T. Morii, D. Roy, K. Sudoh

To test a possible color-octet contribution of heavy quarkonium productions, we propose $ψ$'-productions for small-$p_T$ regions, where the color-singlet $ψ$' state cannot be produced by the gluon-gluon fusion owing to charge conjugation. We also point out that these processes are very useful to deduce informations of spin-dependent gluon distributio

Martin Zach, Manfried Faber, Peter Skala

The dually transformed path integral of four-dimensional U(1) lattice gauge theory is used for the calculation of expectation values in the presence of external charges. Applying the dual simulation to flux tubes for charge distances up to around 20 lattice spacings, we find a deviation from the behaviour of a dual type-II superconductor in the London limit

Chung-I Kuo

We consider vacuum polarization effect of a conformally coupled massless scalar field in the background produced by an idealized straight cosmic string. Using previous criterion we show the calculation of back reaction of the field to the metric in the context of semiclassical gravity theory is not valid , in some regions due to large quantum fluctuations in

Yu. N. Obukhov, E. J. Vlachynsky, W. Esser, F. W. Hehl

The irreducible decomposition technique is applied to the study of classical models of metric-affine gravity (MAG). The dynamics of the gravitational field is described by a 12-parameter Lagrangian encompassing a Hilbert-Einstein term, torsion and nonmetricity square terms, and one quadratic curvature piece that is built up from Weyl's segmental curvatur

Naresh Dadhich

So far all known singularity-free cosmological models are cylindrically symmetric. Here we present a new family of spherically symmetric non-singular models filled with imperfect fluid and radial heat flow, and satisfying the weak and strong energy conditions. For large $t$ anisotropy in pressure and heat flux tend to vanish leading to a perfect fluid. There

Naresh Dadhich

Black hole horizon is usually defined as the limit for existence of timelike worldline or when a spatially bound surface turns oneway (it is crossable only in one direction). It would be insightful and physically appealing to find its characterization involving an energy consideration. By employing the Brown-York [1] quasilocal energy we propose a new and no

S. A. Gogilidze, A. M. Khvedelidze, V. V. Papoyan, Yu. G. Palii

Relations between the Friedmann observables of the expanding Universe and the Dirac observables in the generalized Hamiltonian approach are established for the Friedmann cosmological model of the Universe with the field excitations imitating radiation. A full separation of the physical sector from the gauge one is fulfilled by the method of the gaugeless red

A. M. Khvedelidze, V. V. Papoyan, Yu. G. Palii, V. N. Pervushin

The solution of the problem of describing the Friedmann observables (the Hubble law, the red shift, etc.) in quantum cosmology is proposed on the basis of the method of gaugeless Hamiltonian reduction in which the gravitational part of the energy constraint is considered as a new momentum. We show that the conjugate variable corresponding to the new momentum

Fabrizio Catanese, Claude LeBrun

We show that there are high-dimensional smooth compact manifolds which admit pairs of Einstein metrics for which the scalar curvatures have opposite signs. These are counter-examples to a conjecture considered by Besse. The proof hinges on showing that the Barlow surface has small deformations with ample canonical line bundle.

Mirim Lee, James W. Dufty

The BGK model kinetic equation is applied to spatially inhomogeneous states near steady uniform shear flow. The shear rate of the reference steady state can be large so the states considered include those very far from equilibrium. The single particle distribution function is calculated exactly to first order in the deviations of the hydrodynamic field gradi

Pablo Laguna, Wojciech Zurek

We present results of numerical studies of the Landau-Ginzburg dynamics of the order parameter in one-dimensional models inspired by the condensed matter analogues of cosmological phase transitions. The main goal of our work is to show that, as proposed by one of us \cite{Zurek85b}, the density of the frozen-out topological defects is set by the competition

J. Lleweilun Smith, Qimiao Si

We study the effects of intersite RKKY-like interactions in the mixed valence regime of a two-band extended Hubbard model. This model is known to display a metallic non-Fermi liquid state with spin-charge separation in the standard $D=\infty$ limit (where interactions lead to purely on-site fluctuations only). Using an extended $D=\infty$ approach, we find t

D. L. Feder, A. Beardsall, A. J. Berlinsky, C. Kallin

Twin boundaries in orthorhombic d-wave superconductors are investigated numerically using the Bogoliubov-deGennes formalism within the context of an extended Hubbard model. The twin boundaries are represented by tetragonal regions of variable width, with a reduced chemical potential. For sufficiently large twin boundary width and change in chemical potential

A. Malinowski, Marta Z. Cieplak, A. S. van Steenbergen, J. A. A. J. Perenboom

Magnetoresistance measurements of highly underdoped superconducting La_{2-x}Sr_xCuO_4 films with $x = 0.051$ and $x = 0.048$, performed in dc magnetic fields up to 20 T and at temperatures down to 40 mK, reveal a magnetic-field induced transition from weak to strong localization in the normal state. The normal-state conductances per CuO_2--plane, measured at

M. E. Portnoi, I. Galbraith

The variable-phase approach is applied to scattering and bound states in an attractive Coulomb potential, statically screened by a two-dimensional (2D) electron gas. A 2D formulation of Levinson's theorem is used for bound-state counting and a hitherto undiscovered, simple relationship between the screening length and the number of bound states is found.

E. N. M. Cirillo, G. Gonnella, S. Stramaglia

Results are presented for the kinetics of domain growth of a two-dimensional Ising spin model with competing interactions quenched from a disordered to a striped phase. The domain growth exponent are $β=1/2$ and $β=1/3$ for single-spin-flip and spin-exchange dynamics, as found in previous simulations. However the correlation functions measured in the directi

E. Zaremba, A. Griffin, T. Nikuni

We derive the coupled equations of motion for the condensate (superfluid) and non-condensate (normal fluid) degrees of freedom in a trapped Bose gas at finite temperatures. Our results are based on the Hartree-Fock-Popov approximation for the time-dependent condensate wavefunction and an assumption of local equilibrium for the non-condensate atoms. In the ca

Andr'as Csord'as, Robert Graham, P'eter Sz'epfalusy

The WKB-approximation for the Bogoliubov-equations of the quasi-particle excitations in Bose-gases with condensate is worked out in the case of spherically symmetric trap potentials on the basis of the resulting quantization rule. The excitation spectrum is calculated numerically and also analytically in certain limiting cases. It is found that the energy le

M. Ershov, A. N. Korotkov

The spectral density of current fluctuations in single quantum well infrared photodetectors is calculated using Langevin approach. The noise gain and the photocurrent gain are expressed in terms of basic transport parameters. Fluctuations of the incident photon flux are taken into account.

A. V. Postnikov, A. I. Poteryaev, G. Borstel

Nb-substituting Fe impurity in KNbO3 is studied in first-principles supercell calculations by the linear muffin-tin orbital method. Possible ways to account for the impurity charge compensation are discussed. Calculations are done in the local density approximation (LDA) and, for better description of Coulomb correlation effects within the localized impurity

P. V. Shevchenko, O. P. Sushkov

Implications of the small Fermi surface are discussed. We demonstrate that superconductivity in this system can be described in terms of two coupled condensates. The two condensates result in a collective excitation corresponding to the relative phase oscillation - a phason. We discuss the possibility of searching for this collective excitation in the dynami

Steven R. White, D. J. Scalapino

Using the density matrix renormalization group (DMRG), we study the 2D t-J model at a hole doping of x=1/8 on clusters as large as 19x8. We find a striped phase which is consistent with recent neutron scattering experiments. We find that bond-centered and site-centered stripes have nearly the same energy, suggesting that in the absence of pinning effects the

Ian Affleck

The excitation spectrum of spin-Peierls antiferromagnets is discussed taking into acount phonon dynamics but treating inter-chain elastic couplings in mean field theory. This gives a ladder of soliton -anti-soliton boundstates, with no soliton continuum, until soliton deconfinement takes place at a transition into a non-dimerized phase.

Efthimios Kaxiras

We discuss a generalization of the surface reconstruction arguments for the structure of intermediate size Si clusters, which leads to model geometries for the sizes 33, 39 (two isomers), 45 (two isomers), 49 (two isomers), 57 and 61 (two isomers). The common feature in all these models is a structure that closely resembles the most stable reconstruction of

Paul Buitelaar

The paper defends the notion that semantic tagging should be viewed as more than disambiguation between senses. Instead, semantic tagging should be a first step in the interpretation process by assigning each lexical item a representation of all of its systematically related senses, from which further semantic processing steps can derive discourse dependent

James B. Dove, Jorn Wilms, Mitchell C. Begelman

We present the properties of accretion disk corona (ADC) models, where the radiation field, the temperature, and the total opacity of the corona are determined self-consistently. We use a non-linear Monte Carlo code to perform the calculations. As an example, we discuss models where the corona is situated above and below a cold accretion disk with a plane-pa

Craig J. Hogan, Keith A. Olive, Sean T. Scully

We introduce a new statistical method to estimate the primordial helium abundance, Y_p from observed abundances in a sample of galaxies which have experienced stellar helium enrichment. Rather than using linear regression on metal abundance we construct a likelihood function using a Bayesian prior, where the key assumption is that the true helium abundance m

A. D. Schwope, D. A. H. Buckley, D. O'Donoghue, G. Hasinger

We report phase-resolved optical polarimetric, photometric and spectroscopic observations of RX J2115.7-5840 (= EUVE J2115-58.6, Craig 1996) which confirms the system to be a magnetic cataclysmic binary of the polar (AM Herculis) subclass. The optical light curve is sometimes flat and occasionally displays a pronounced bright phase, reminiscent of the self-e

G. L. Israel, L. Stella, L. Angelini, N. E. White

During a systematic search for periodic signals in a sample of ROSAT PSPC light curves, we discovered ~ 8.9s X-ray pulsations in 2E0050.1-7247, a variable X-ray source in the Small Magellanic Cloud. The source was detected several times between 1979 and 1993 at luminosity levels ranging from about 5 times 10^{34} erg/s up to 1.4 times 10^{36} erg/s with both

Brad K. Gibson

We consider the simultaneous chemical, photometric, and gaseous thermal energy evolution of elliptical galaxies. The evolution of chemical abundances in the intracluster medium (ICM) is set by the differing timescales for gas ejection, via supernovae (SNe)-driven winds, from dwarf, normal, and giant ellipticals, and is monitored concurrently. Emphasis is pla

C. D. Dermer, J. Bland-Hawthorn, J. Chiang, K. McNaron-Brown

We report results of soft gamma-ray observations of the ultraluminous infrared galaxies Arp 220, Mrk 273, and Mrk 231 in order to test whether the infrared radiation from these sources originates from buried active galactic nuclei (AGNs). Only upper limits are measured, implying that the emergent soft gamma-ray luminosities are 1-2 orders of magnitude smalle

Nino Boccara, Henryk Fuks

We present a family of one-dimensional cellular automata modeling the diffusion of an innovation in a population. Starting from simple deterministic rules, we construct models parameterized by the interaction range and exhibiting a second-order phase transition. We show that the number of individuals who eventually keep adopting the innovation strongly depen

Henryk Fuks, Nino Boccara

We study a family of deterministic models for highway traffic flow which generalize cellular automaton rule 184. This family is parametrized by the speed limit $m$ and another parameter $k$ that represents a ``degree of aggressiveness'' in driving, strictly related to the distance between two consecutive cars. We compare two driving strategies with i

Glenn P. Tiede, Paul Martini, Jay A. Frogel

We apply the giant branch slope-[Fe/H] relation derived by Kuchinski et al. [AJ, 109, 1131 (1995)] to a sample of open clusters. We find that the slope of the giant branch in K vs. (J-K) color-magnitude diagrams correlates with [Fe/H] for open clusters as it does for metal-rich globular clusters but that the open cluster data are systematically shifted to le

P. S. Howe, E. Sezgin, P. C. West

Some aspects of the geometry of superembeddings and its application to supersymmetric extended objects are discussed. In particular, the embeddings of (3|16) and (6|16) dimensional superspaces into (11|32) dimensional superspace, corresponding to supermembranes and superfivebranes in eleven dimensions, are treated in some detail.

W. de Boer

Electroweak precision tests of the SM and MSSM as well as searches for Supersymmetric Particles and Higgs bosons at LEP II and their significance within the MSSM are discussed. Invited talk presented at the EPIPHANY Conf. in Cracow, Jan. 3-7, 1997.

Katrin Becker, Melanie Becker

We consider the scattering of two Dirichlet zero-branes in M(atrix) theory. Using the formulation of M(atrix) theory in terms of ten-dimensional super Yang-Mills theory dimensionally reduced to $(0+1)$-dimensions, we obtain the effective (velocity dependent) potential describing these particles. At one-loop we obtain the well known result for the leading ord

Dietmar Weinmann, Jean-Louis Pichard, Yoseph Imry

Considering N spinless Fermions in a random potential, we study how a short range pairwise interaction delocalizes the N-body states in the basis of the one-particle Slater determinants, and the spectral rigidity of the N-body spectrum. The maximum number g_N of consecutive levels exhibiting the universal Wigner-Dyson rigidity (the Thouless number) is given

George F. Smoot

This paper given at the Strasbourg NATO school on the CMB and cosmology reports the contents of four hours of lectures on the CMB spectrum, potential distortions, and implications. It was followed by 6 hours of lectures on CMB anisotropy. This paper reviews the observations and theoretical implications for the CMB frequency spectrum - both for the monopole (

Alexander K. Guts

Can the Past be restored? Poincaré and Costa de Beauregard showed that the past is not restored statistically. This follows from Bayes formula. In given note two new Principles are postulated which forbid the restoration of the Past.

Jacek Generowicz, Chris Harvey-Fros, Tim R. Morris

Within the Local Potential Approximation to Wilson's, or Polchinski's, exact renormalization group, and for general spacetime dimension, we construct a function, c, of the coupling constants; it has the property that (for unitary theories) it decreases monotonically along flows, and is stationary only at fixed points ---where it `counts degrees of fr

Dimitra Karabali, Chanju Kim, V. P. Nair

We carry out the Hamiltonian analysis of non-Abelian gauge theories in (2+1) dimensions in a gauge-invariant matrix parametrization of the fields. A detailed discussion of regularization issues and the construction of the renormalized Laplace operator on the configuration space, which is proportional to the kinetic energy, are given. The origin of the mass g

A. Gehrmann-De Ridder, T. Gehrmann, E. W. N. Glover

We present the results of a calculation of the rate for the annihilation of an $e^+e^-$ pair into a jet containing an energetic photon and a single further jet at order $αα_{s}$. By comparing these results with the existing data on the photon + 1 jet rate from the ALEPH Collaboration, we make a first determination of the process independent quark-to-photon f

C. Fuchs, P. Essler, T. Gaitanos, H. H. Wolter

We investigate thermodynamic properties and instability conditions in intermediate energy heavy ion reactions. We define locally thermodynamic variables, i.e. density, pressure and temperature, directly from the phase space distribution of a relativistic transport calculation. In particular, temperatures are determined by a fit to two covariant hot Fermi dis

Guillermo A. Mena Marugan

In the Ashtekar and geometrodynamic formulations of vacuum general relativity, the Euclidean and Lorentzian sectors can be related by means of the generalized Wick transform discovered by Thiemann. For some vacuum gravitational systems in which there exists an intrinsic time variable which is not invariant under constant rescalings of the metric, we show tha

P. Bressler, R. Nest, B. Tsygan

We give a proof of a conjecture of P. Schapira and J.-P. Schneiders on the characteristic classes of D-modules.

Saul Barshay, Georg Kreyerhoff

We show that the axial-vector coupling of Z0(W+-) to quarks, when acting together with the emission of a hypothetical spin-zero jet-generating quantum coupled to quarks results in an unusual behavior in certain processes, at high energy and momentum transfer. This involves an excess jet production at the subpicobarn level.

S. Das Sarma

A review is provided of our current theoretical understanding of dynamic scaling in nonequilibrium interface growth as, for example, in MBE growth under ultrahigh vacuum deposition conditions.

S. M. Bilenky, C. Giunti, W. Grimus

We consider long-baseline neutrino oscillations in the framework of two schemes with mixing of four massive neutrinos which can accommodate all the existing indications in favour of neutrino mixing. Within these schemes, we derive bounds on the oscillation probabilities and the CP-odd neutrino-antineutrino asymmetries in long-baseline experiments. Using the

V. Musolino, A. Selloni, R. Car

We present a density functional study of the structural and electronic properties of small Cu_n (n=1,4) aggregates on defect-free MgO(100). The calculations employ a slab geometry with periodic boundary conditions, supercells with up to 76 atoms, and include full relaxation of the surface layer and of all adsorbed atoms. The preferred adsorption site for a s

Joerg Neugebauer, Tosja Zywietz, Matthias Scheffler, John E. Northrup

We have investigated clean and As-covered zinc-blende GaN (001) surfaces, employing first-principles total-energy calculations. For clean GaN surfaces our results reveal a novel surface structure very different from the well-established dimer structures commonly observed on polar III-V (001) surfaces: The energetically most stable surface is achieved by a Pe

F. Courbin, P. Magain, C. R. Keeton, C. S. Kochanek

Time delay measurements have recently been reported for the lensed quasar PG 1115+080. These measurements can be used to derive Ho, but only if we can constrain the lensing potential. We have applied a recently developed deconvolution technique to analyse sub-arcsecond I band images of PG 1115+080, obtained at the Nordic Optical Telescope (NOT) and the Canad

D. Song

The paper has been withdrawn by the author.

Kensuke Kusaka, Ken Simpson, Anthony G. Williams

We apply the perturbation theory integral representation (PTIR) to solve for the bound state Bethe-Salpeter (BS) vertex for an arbitrary scattering kernel, without the need for any Wick rotation. The results derived are applicable to any scalar field theory (without derivative coupling). It is shown that solving directly for the BS vertex, rather than the BS

Vladimir Privman, Dima Mozyrsky, Steven P. Hotaling

We argue that the analog nature of quantum computing makes the usual design approach of constructing complicated logical operations from many simple gates inappropriate. Instead, we propose to design multi-spin quantum gates in which the input and output two-state systems (spins) are not necessarily identical. We outline the design criteria for such devices

G. M. D'Ariano, M. G. A. Paris

Random-phase homodyne tomography of the field intensity is a concrete example of the Quantum Roulette of Helstrom. In this paper we give the explicit POM of such measurement and compare it with direct photodetection and heterodyne detection. Effects of nonunit quantum efficiency are also considered. Naimark extensions for the roulette POM are analyzed and it

Joseph Samuel, Supurna Sinha

We describe a non-Abelian Berry phase in polarisation optics, suggested by an analogy due to Nityananda between boosts in special relativity and the effect of elliptic dichroism on polarised light. The analogy permits a simple optical realization of the non-Abelian gauge field describing Thomas rotation. We also show how Thomas rotation can be understood geo

John C. Baez

An n-category is some sort of algebraic structure consisting of objects, morphisms between objects, 2-morphisms between morphisms, and so on up to n-morphisms, together with various ways of composing them. We survey various concepts of n-category, with an emphasis on `weak' n-categories, in which all rules governing the composition of j-morphisms hold on

Boaz Tsaban

Hurewicz found connections between some topological notions and the combinatorial cardinals b and d. Reclaw gave topological meaning to the definition of the cardinal p. We extend the picture with a topological interpretation of the cardinal t. We compare our notion to the one related to p, and to some other classical notions. This sheds new light on the fam

John H. Schwarz

Brane actions with chiral bosons present special challenges. Recent progress in the description of the two main examples -- the M theory five-brane and the heterotic string -- is described. Also, double dimensional reduction of the M theory five-brane on K3 is shown to give the heterotic string.

D. Buchholz, S. Doplicher, G. Morchio, J. E. Roberts

We discuss a simple but instructive model in which Gauss' law holds for a class of charged states. In spite of the non-localizability of these charges, the corresponding superselection sectors can be labelled by the spectrum of some internal symmetry group and have well defined statistics. More interestingly, the properties of these charged states seem t

K. N. Ilinski, G. V. Kalinin, A. S. Stepanenko

In the paper we give consecutive description of functional methods of quantum field theory for systems of interacting q-particles. These particles obey exotic statistics and appear in many problems of condensed matter physics, magnetism and quantum optics. Motivated by the general ideas of standard field theory we derive formulae in q-functional derivatives

U. H. Danielsson, G. Ferretti, I. R. Klebanov

We study the force balance between orthogonally positioned $p$-brane and $(8-p)$-brane. The force due to graviton and dilaton exchange is repulsive in this case. We identify the attractive force that balances this repulsion as due to one-half of a fundamental string stretched between the branes. As the $p$-brane passes through the $(8-p)$-brane, the connecti

Brandon Carter

It is shown how a pure background tensor formalism provides a concise but explicit and highly flexible machinery for the generalised curvature analysis of individual embedded surfaces and foliations such as arise in the theory of topological defects in cosmological and other physical contexts. The unified treatment provided here shows how the relevant extens

A. Yu. Segal, A. A. Sharapov

The coherent states associated to the discrete serie representations $D(E_o,s)$ of $SO(3,2)$ are constructed in terms of (spin-)tensor fields on $D=4$ anti-de Sitter space. For $E_o>s+5$ the linear space ${\cal H}_{E_o,s}$ spanned by these states is proved to carry the unitary irreducible representation $D(E_o,s)$. The $SO(3,2) $-covariant generalized Fourie

J. H. Lorentsen, N. K. Nielsen

A massive relativistic spinning point particle in any number of dimensions has in a previous article been shown to be described by first class constraints, which define a gauge theory. In the present paper we find the corresponding finite gauge transformations. By comparing the integrated gauge transformations to transformation equations found by Pryce, we c

Philip Baringer, Pankaj Jain, Douglas W. Mckay, Lesley L. Smith

We investigate the contribution of technicolor mechanisms to the production of single top quarks at hadron colliders. Technipions with mass larger than the top mass will decay predominantly to a top quark plus a bottom antiquark. We investigate two promising sub-processes: technipion plus W-boson via gluon-gluon fusion and technipion plus quark production vi

Savas Dimopoulos, Gia Dvali, Riccardo Rattazzi, Gian Giudice

We construct a class of simple and calculable theories for the supersymmetry breaking soft terms. They are based on quantum modified moduli spaces. These theories do not break supersymmetry in their ground state; instead we postulate that we live in a supersymmetry breaking plateau of false vacua. We demonstrate that tunneling from the plateau to the supersy

Alessandro Strumia

We show that gauge-mediation and unified-supergravity give sufficiently firm and different predictions for the spectrum of supersymmetric particles to make it possible to discriminate the two scenarios even if the messenger mass is close to the unification scale.

Konstantinos Dimopoulos, Anne-Christine Davis

We investigate the evolution of a superconducting string network with arbitrary, constant string current in the friction dominated regime. In the absence of an external magnetic field the network always reaches a scaling solution. However, for string current stronger than a critical value, it is different than the usual, horizon-scaling of the non-supercondu

J. R. Pelaez

The low energy dynamics of the general strongly interacting symmetry breaking sector can be easily described using effective chiral Lagrangians. Indeed, the enhancement in WW scattering at LHC, that would imply the existence of such an strong interaction, can be described with just two chiral parameters. These techniques have been shown to reproduce remarkab

P. Rehberg, Yu. L. Kalinovsky, D. Blaschke

At the Mott transition of a quark/meson plasma, mesons become unbound. This leads to the effect of critical scattering, which is studied by investigating photon pair production due to the process $q\bar q\toγγ$. This process can proceed either via direct annihilation or via the formation of a mesonic resonance. It is shown that the latter channel leads to an

Junko Shigemitsu

Recent results for B meson decay constants with NRQCD b-quarks and clover light quarks are discussed. Perturbative matching factors through O($α/M$) are now available and incorporated into the analyses. An O($αa$) improvement term to the heavy-light axial current is identified and included. The slope of $f_{PS}\sqrt{M_{PS}}$ versus $1/M_{PS}$ is significantl