July 1996 arXiv papers — page 10

S. H. Rhie, D. P. Bennett

Gravitational microlensing is known for baryoninc dark matter searches. Here we show that microlensing also provides a unique tool for the detection of low mass planets (such as earths and neptunes) from the ground. A planetary system forms a binary lens (or, a multi-point lens), and we can determine the mass ratio of the planet with respect to the star and

A. B. Harris, Randall D. Kamien, T. C. Lubensky

We present a microscopic analysis of the instability of the nematic phase to chirality when molecular chirality is introduced perturbatively. We show that previously neglected short-range biaxial correlations play a crucial role in determining the cholesteric pitch. We propose an order parameter which quantifies the chirality of a molecule.

R. Donagi, A. Grassi, E. Witten

We compute the non-perturbative superpotential in $F$-theory compactification to four dimensions on a complex three-fold $¶^1\times S$, where $S$ is a rational elliptic surface. In contrast to examples considered previously, the superpotential in this case has interesting modular properties; it is essentially an $E_8$ theta function.

Alon E. Faraggi

Recently there has been a resurgence of interest in gauge mediated dynamical supersymmetry breaking scenarios. I investigate how low energy dynamical SUSY breaking may arise from superstring models. In a three generation string derived model I propose that the unbroken hidden non--Abelian gauge group at the string scale is $SU(3)_H$ with matter multiplets. D

Joao M. Soares

The Cabibbo-Kobayashi-Maskawa matrix element |V_ub| can be extracted from the rate for the semi-leptonic decay B -> pi + l + antineutrino_l, with little theoretical uncertainty, provided the hadronic form factor for the B -> pi transition can be measured from some other B decay. In here, we suggest using the decay B -> pi Jψ. This is a color suppressed decay

Michael Dine

For a long time, it has been widely assumed that if the underlying laws of nature are supersymmetric, supersymmetry is broken at a scale intermediate between the weak scale and the Planck mass. The construction of realistic models of dynamical supersymmetry breaking in which supersymmetry is broken at a much lower scale, as well as a growing appreciation of

F. Gonzalez-Rey, U. Lindstrom, M. Rocek, R. von Unge

We propose a Wilsonian action compatible with special geometry and higher dimension N=2 corrections, and show that the holomorphic contribution F to the low energy effective action is independent of the infrared cutoff. We further show that for asymptotically free SU(2) super Yang-Mills theories, the infrared cutoff can be tuned to cancel leading corrections

N. J. Cerf, J. Boutet de Monvel, O. Bohigas, O. C. Martin

The traveling salesman problem (TSP) consists of finding the length of the shortest closed tour visiting N ``cities''. We consider the Euclidean TSP where the cities are distributed randomly and independently in a d-dimensional unit hypercube. Working with periodic boundary conditions and inspired by a remarkable universality in the kth nearest neigh

Stefano Forte, Richard D. Ball

We discuss the theoretical implications of the scaling properties of F_2^p at small x observed in recent HERA experiments. We show that low Q^2 data display double scaling violations which are adequately described by NL ln Q^2 corrections. Scaling violations due to summations of leading and subleading ln 1/x beyond NLO in ln Q^2 are however disfavoured by th

Raimar Wulkenhaar

We develop a mathematical concept towards gauge field theories based upon a Hilbert space endowed with a representation of a skew-adjoint Lie algebra and an action of a generalized Dirac operator. This concept shares common features with the non-commutative geometry a la Connes/Lott, differs from that, however, by the implementation of skew-adjoint Lie algeb

Moshe Havilio

It is shown that the problem of calculating spin-spin correlation functions, in the dimers RVB states, on a possibly diluted 2D square lattice, can be formulated in terms of a transfer matrix. The transfer matrix is used for exact numerical calculations of spin-spin correlation functions on ladders up to four units wide.

W. Buchmuller, A. Hebecker, M. F. McDermott

Order $α_s$-corrections to the diffractive structure functions $F_L^D$ and $F_2^D$ at large $Q^2$ and small $x$ are evaluated in the semiclassical approach, where the initial proton is treated as a classical colour field. The diffractive final state contains a fast gluon in addition to a quark-antiquark pair. Two of these partons may have large transverse mo

Michal Horodecki, Pawel Horodecki, Ryszard Horodecki

We apply the inseparability criterion for $2 \times 2$ systems, local filtering and Bennett et al. purification protocol [Phys. Rev. Lett. {\bf 76}, 722 (1996)] to show how to distill {\it any} inseparable $2\times 2$ system. The extended protocol is illustrated geometrically by means of the state parameters in the Hilbert-Schmidt space.

A. Liguori, M. Mintchev, L. Zhao

Some algebraic aspects of field quantization in space-time with boundaries are discussed. We introduce an associative algebra, whose exchange properties are inferred from the scattering processes in integrable models with reflecting boundary conditions on the half line. The basic properties of this algebra are established and the Fock representations associa

Mohan Narayan, G. Rajasekaran, S. Uma Sankar

We analyze the atmospheric neutrino data in the context of three flavor neutrino oscillations taking account of the matter effects in the earth. With the hierarchy among the vacuum mass eigenvalues $μ_3^2 \gg μ_2^2 \geq μ_1^2$, the solution of the atmospheric neutrino problem depends on $δ_{31}=μ_3^2 - μ_1^2$ and the $13$ and $23$ mixing angles $ϕ$ and $ψ$.

U. Zuelicke, A. H. MacDonald

We have evaluated wavevector-dependent electronic spectral functions for integer and fractional quantum Hall edge states using a chiral Luttinger liquid model. The spectral functions have a finite width and a complicated line shape because of the long-range of the Coulomb interaction. We discuss the possibility of probing these line shapes in vertical tunnel

J. J. Betouras, R. Joynt, Z. -W. Dong, T. Venkatesan

A theoretical model of high-T_c Josephson Field Effect Transistors (JoFETs) based on a Ginzburg-Landau free energy expression whose parameters are field- and spatially- dependent is developed. This model is used to explain experimental data on JoFETs made by the hole-overdoped Ca-SBCO bicrystal junctions (three terminal devices). The measurements showed a la

C. B. Muratov, V. V. Osipov

We performed an extensive numerical study of a two-dimensional reaction-diffusion system of the activator-inhibitor type in which domain patterns can form. We showed that both multidomain and labyrinthine patterns may form spontaneously as a result of Turing instability. In the stable homogeneous system with the fast inhibitor one can excite both localized a

S. Das Gupta, J. Pan, I. Kvasnikova, C. Gale

We establish links between three different models for multifragmentation: the percolation model, the lattice gas model and the statistical multifragmentation model. There are remarkable similarities between the lattice gas model and the statistical multifragmentation model. For completeness, we also compare with a model based upon classical molecular dynamic

J. Haidenbauer, Ch. Hanhart, J. Speth

A brief overview on recent model calculations for near threshold pion production in nucleon-nucleon collisions is given. Results from our own investigations of the reactions $pp \rightarrow ppπ^0$ and $pn \rightarrow dπ^0$ are presented. Direct production, heavy meson exchange and pion rescattering are taken into account. For the latter a T-matrix obtained f

J. Konopka, S. A. Bass, M. Bleicher, M. Brandstetter C. Ernst

Quantum Molecular Dynamics (QMD) calculations of central collisions between heavy nuclei are used to study fragment production and the creation of collective flow. It is shown that the final phase space distributions are compatible with the expectations from a thermally equilibrated source, which in addition exhibits a collective transverse expansion. Howeve

Jens Konopka, Horst Stoecker, Walter Greiner

Quantum Molecular Dynamics (QMD) calculations are used to study the expansion phase in central collisions between heavy nuclei. The final state of such a reaction can be understood as the result of a entropy conserving expansion starting from a compact source. The properties of this hypothetic source, however, are in conflict with the assumptions used in fir

Byung Deok Yu, Matthias Scheffler

The growth morphology of clean silver exhibits a profound anisotropy: The growing surface of Ag(111) is typically very rough while that of Ag(100) is smooth and flat. This serious and important difference is unexpected, not understood, and hitherto not observed for any other metal. Using density functional theory calculations of self-diffusion on flat and st

George Androulakis, C. D. Cazacu, Nigel J. Kalton

We study certain twisted sums of Orlicz spaces with non-trivial type which can be viewed as Fenchel-Orlicz spaces on ${\rm {\bf R}}^2$. We then show that a large class of Fenchel-Orlicz spaces on ${\rm {\bf R}}^n$ can be renormed to have property (M). In particular this gives a new construction of the twisted Hilbert space $Z_2$ and shows it has property (M)

M. C. Diamantini

We study phase transitions induced by topological defects in Abelian gauge theories of open p-branes in (d+1) space-time dimensions. Starting from a massive antisymmetric tensor theory for open p-branes we show how the condensation of topological defects can lead to a decoupled phase with a massless tensor coupled to closed (p-1)-branes and a massive tensor

J. E. Paschalis, P. I. Porfyriadis

The two flavour, four dimensional WZW model coupled to electromagnetism, is treated as a constraint system in the context of the Faddeev-Jackiw approach. No approximation is made. Detailed exposition of the calculations is given. Solution of the constraints followed by proper Darboux's transformations leads to an unconstrained Coulomb-gauge Lagrangian de

S. Mallik, K. Mukherjee

We calculate the self-energy at finite temperature in scalar $λϕ^4$ theory to second order in a modified perturbation expansion. Using the renormalisation group equation to tame the logarithms in momentum, it gives an equation to determine the critical temperature. Due to the infrared freedom of the theory, this equation is satisfied, irrespective of the val

M. Svec

The measurements of reactions $π^- p_\uparrow \to π^- π^+ n$ at 17.2 GeV/c and $π^+ n_\uparrow \to π^+ π^- p$ at 5.98 and 11.85 GeV/c made at CERN with polarized targets provide a model-independent and solution-independent evidence for a narrow scalar state sigma(750). The original chi^2 minimization method and the recent Monte Carlo method for amplitude ana

S. Veseli, I. Dunietz

We investigate decay constants of P and D-wave heavy-light mesons within the mock-meson approach. Numerical estimates are obtained using the relativistic quark model. We also comment on recent calculations of heavy-light pseudo-scalar and vector decay constants.

John Ellis, Toby Falk, Keith Olive, Michael Schmitt

We discuss the lower limit on the mass of the neutralino $χ$ that can be obtained by combining data from $e^+e^-$ annihilation at LEP and elsewhere with astrophysical and theoretical considerations. Loopholes in the purely experimental analysis of ALEPH data from the Z peak and LEP 1.5, which appear when $μ<0$ for certain values of the sneutrino mass $m_{\ti

Richard D. Ball, Stefano Forte

We describe the measurement of the strong coupling alpha_s from data on inclusive DIS at high energies. We present new results using the 1994 data from H1, and confirm directly the expected running of alpha_s.

A. Ballestrero, E. Maina, M. Pizzio

We compute complete tree level matrix elements for $gg , q \bar q \rightarrow b \bar b W^+W^-$. We analyze the irreducible backgrounds to top signal at the Tevatron and at the LHC. Their contribution to the total cross section is about $5 \%$ at the LHC, due to single resonant channels. Several distributions with contributions from signal and backgrounds are

Alexander Kusenko

The scalar potential of theories with broken supersymmetry can have a number of local minima characterized by different gauge groups. Symmetry properties of the physical vacuum constrain the parameters of the MSSM. We discuss these constraints, in particular those that result from the vacuum stability with respect to quantum tunneling.

V. Agostini, G. Carlino, M. Caselle, M. Hasenbusch

We present a high precision Monte Carlo study of the spectrum of the $Z_2$ gauge theory in $2+1$ dimensions in the strong coupling phase. Using state of the art Monte Carlo techniques we are able to accurately determine up to three masses in a single channel. We compare our results with the strong coupling expansion for the lightest mass and with results for

The ALEPH Collaboration

Indirect limits on the mass of the lightest neutralino are derived from the results of searches for charginos, neutralinos, and sleptons performed with data taken by the ALEPH Collaboration at centre-of-mass energies near the Z peak and at 130 and 136 GeV. Within the context of the Minimal Supersymmetric Standard Model and when $M_{\tildeν}\ge 200$ GeV/c^2,

SLD Collaboration

We present the first study of rapidity gaps in e+e- annihilations using Z0 decays collected by the SLD experiment at SLAC. Our measured rapidity gap spectra fall exponentially with increasing gap size over five decades, and we observe no anomalous class of events containing large gaps. This supports the interpretation of the large-gap events measured in pp a

Gary T. Horowitz, Harrison J. Sheinblatt

The Ernst spacetime is a solution of the Einstein-Maxwell equations describing two charged black holes accelerating apart in a uniform electric (or magnetic) field. As the field approaches a critical value, the black hole horizon appears to touch the acceleration horizon. We show that weak cosmic censorship cannot be violated by increasing the field past thi

Dieter Brill

Lecture given at ``Raychaudhuri session,&#34; ICGC-95 conference, Pune (India), December 1995. Contents: I. Introduction II. (2+1)-Dimensional Initial Values in Stereographic Projection A. The single, non-rotating black hole B. Non-rotating multi-black-holes C. ``Black Hole&#34; Universe Initial Values III. Time Development: Enter the Raychaudhuri Equation I

Luc Blanchet

1. Introduction 2. Basics and outline of the method 2.1 Regions around an isolated source 2.2 The quadrupole formalism 2.3 Outline of the method 3. Properties of radiative gravitational fields 3.1 The field in the exterior domain (D_e) 3.2 Computing the field nonlinearities in (D_e) 3.3 The field in the far wave zone D_w 3.4 Nonlinear effects in the far-zone

Philip Phillips, Nancy Sandler

We derive here a stability condition for a local moment in the presence of an interacting sea of conduction electrons. The conduction electrons are modeled as a Luttinger liquid in which chirality and spin are coupled. We show that an Anderson-U defect in such an interacting system can be transformed onto a nearly-Fermi liquid problem. We find that correlati

Yigal Meir

A universal scaling function, describing the crossover between the Mott and the Efros-Shklovskii hopping regimes, is derived, using the percolation picture of transport in strongly localized systems. This function is agrees very well with experimental data. Quantitative comparison with experiment allows for the possible determination of the role played by po

Stéphane Cueille, Clément Sire

We study a Smoluchowski equation describing a simple mean-field model of particles moving in $d$ dimensions and aggregating with conservation of `mass&#39; $s=R^D$ ($R$ is the particle radius). In the scaling regime the scaled mass distribution $P(s)\sim s^{-τ}$, and $τ$ can be computed by perturbative and non perturbative expansions. A possible application

A. Martin-Rodero, A. Levy Yeyati, F. J. Garcia-Vidal, J. C. Cuevas

This manuscript contains a Comment on &#34;Supercurrent Noise in Quantum Point Contacts&#34; by D. Averin and H.T. Iman, Phys. Rev. Lett. 76, 3814 (1996) [cond-mat/9511128].

Pierre-Antoine Rey, Michel Droz, Jaroslaw Piasecki

We study the possibility of localization of the front present in a one-dimensional ballistically-controlled annihilation model in which the two annihilating species are initially spatially separated. We construct two different classes of initial conditions, for which the front remains localized.

P. Di Francesco, E. Guitter, S. Mori

We study the problem of folding of the regular triangular lattice in the presence of a quenched random bending rigidity + or - K and a magnetic field h (conjugate to the local normal vectors to the triangles). The randomness in the bending energy can be understood as arising from a prior marking of the lattice with quenched creases on which folds are favored

Walter Daelemans, Peter Berck, Steven Gillis

We describe a case study in the application of {\em symbolic machine learning} techniques for the discovery of linguistic rules and categories. A supervised rule induction algorithm is used to learn to predict the correct diminutive suffix given the phonological representation of Dutch nouns. The system produces rules which are comparable to rules proposed b

Walter Daelemans, Jakub Zavrel, Peter Berck, Steven Gillis

We introduce a memory-based approach to part of speech tagging. Memory-based learning is a form of supervised learning based on similarity-based reasoning. The part of speech tag of a word in a particular context is extrapolated from the most similar cases held in memory. Supervised learning approaches are useful when a tagged corpus is available as an examp

Koichi Takeda

This paper proposes the use of ``pattern-based&#39;&#39; context-free grammars as a basis for building machine translation (MT) systems, which are now being adopted as personal tools by a broad range of users in the cyberspace society. We discuss major requirements for such tools, including easy customization for diverse domains, the efficiency of the transl

Eli Waxman, Jordi Miralda-Escude

It has recently been shown that the highest energy cosmic rays (CRs) may originate in the same cosmological objects producing $γ$-ray bursts. This model requires the presence of intergalactic magnetic fields (IGMF) to delay the arrival times of $\sim 10^{20}$ eV CRs by 50 years or longer relative to the $γ$-rays, of an amplitude that is consistent with other

S. A. Laurent-Muehleisen, R. I. Kollgaard, P. J. Ryan, E. D. Feigelson

We present 5 GHz high resolution VLA observations of 2,127 radio- and X-ray-emitting sources found in both the Green Bank (GB) 5 GHz radio catalog and the ROSAT All-Sky Survey (RASS). We report core flux densities and positions accurate to +/-0.5&#34;. Combined with the GB measuremens of the total radio emission, we derive the core-to-lobe ratio of objects i

Jonathan Ferreira

Non-relativistic, magnetically-driven jets are constructed by taking self-consistently into account the feedback on the underlying accretion disc. It is shown that such jets are mostly described by the ejection index $ξ= \mbox{d} \ln \dot M_a/ \mbox{d}\ln r$, which is a local measure of the disc ejection efficiency. This parameter is found to lie in a very n

C. M. Baugh, S. Cole, C. S. Frenk

The unprecedented resolution of the refurbished Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST) has led to major advances in our understanding of galaxy formation. The high image quality in the Medium Deep Survey and Hubble Deep Field has made it possible, for the first time, to classify faint distant galaxies according to morph

Dongsu Ryu, Sandip K. Chakrabarti, Diego Molteni

We characterize the nature of thin, axisymmetric, inviscid, accretion flows of cold adiabatic gas with zero specific energy in the vicinity of a black hole by the specific angular momentum. Using two-dimensional hydrodynamic simulations in cylindrical geometry, we present various regimes in which the accretion flows behave distinctly differently. When the fl

Sergey S. Kurennoy

A method for calculating coupling impedances and power losses for off-axis beams is developed. It is applied to calculate impedances of small localized discontinuities like holes and slots, as well as the impedance due to a finite resistivity of chamber walls, in homogeneous chambers with an arbitrary shape of the chamber cross section. The approach requires

Cheuk-Yin Wong

The anomalous J/psi suppression in Pb-Pb collisions at 158A GeV observed recently by NA50 can be explained as due to the transition to a new phase of strong J/psi absorption, which sets in when the local energy density exceeds about 3.4 GeV/fm**3.

G. Barenboim, M. Raidal

We argue that large non-decoupling effects of heavy neutrinos can appear naturally in manifestly left-right symmetric models due to the minimization conditions of the scalar potential and the structure of vev&#39;s imposed by phenomenology. We derive constraints on off-diagonal light-heavy and heavy-heavy neutrino mixings from the searches for lepton violati

Martina M. Brisudova, Robert J. Perry, Kenneth G. Wilson

A constituent parton picture of hadrons with logarithmic confinement naturally arises in weak coupling light-front QCD. Confinement provides a mass gap that allows the constituent picture to emerge. The effective renormalized Hamiltonian is computed to ${\cal O}(g^2)$, and used to study charmonium and bottomonium. Radial and angular excitations can be used t

J. Avan, A. Jevicki, J. Lee

We extend our study of the field-theoretic description of matrix-vector models and the associated many-body problems of one dimensional particles with spin. We construct their Yangian-su(R) invariant Hamiltonian. It describes an interacting theory of a c=1 collective boson and a k=1 su(R) current algebra. When $R \geq 3$ cubic-current terms arise. Their coup

M. Porrati

We prove in two different ways that brane dynamics gives rise to all H-monopoles predicted by S-duality of N=4, 4-dimensional superstring compactifications. One method uses heterotic-type II duality and the self-dual 3-brane dynamics, the other uses the 5-brane description of small instantons in SO(32) superstrings.

D. L. Bennett, H. B. Nielsen

We calculate the $U(1)$ continuum gauge coupling using the values of action parameters at the multiple point in the phase diagram of a lattice gauge theory. The multiple point is where a maximum number of phases convene. We obtain for the running inverse finestructure constant the values $α_1^{-1}=56\pm 5$ and $α_1^{-1}=99\pm 5$ at respectively the Planck sc

A. V. Sidorov

The QCD analysis of the $xF_3$ structure function measured in deep-inelastic scattering of neutrinos and antineutrinos on an iron target at the Fermilab Tevatron is done in 1--, 2-- and 3--loop order of QCD. The x dependence of the higher--twist contribution is evaluated. The experimental value of higher--twist corrections to the Gross--Llewellyn Smith sum r

S. F. Burlatsky, M. Moreau

We present simple explicit estimates for the apparent reaction rate constant for three molecular reactions, which are important in catalysis. For small concentrations and $d> 1$, the apparent reaction rate constant depends only on the diffusion coefficients and sizes of the particles. For small concentrations and $d\le 1$, it is also time -- dependent. For l

Roland A. Puntigam, Claus Lämmerzahl, Friedrich W. Hehl

The form of Maxwell&#39;s theory is well known in the framework of general relativity, a fact that is related to the applicability of the principle of equivalence to electromagnetic phenomena. We pose the question whether this form changes if torsion and/or nonmetricity fields are allowed for in spacetime. Starting from the conservation laws of electric char

Toshiya Kawai

Tests of duality between heterotic strings on $K3\times T^2$ (restricted on certain Narain moduli subspaces) and type IIA strings on K3-fibered Calabi-Yau threefolds are attempted in the weak coupling regime on the heterotic side by identifying pertinent modular forms related to the computations of string threshold corrections. Concretely we discuss in paral

Renata Kallosh, Marina Shmakova, Wing Kai Wong

In N=2 ungauged supergravity we have found the most general double-extreme dyonic black holes with arbitrary number n_v of constant vector multiplets and n_h of constant hypermultiplets. They are double-extreme: 1) supersymmetric with coinciding horizons, 2) the mass for a given set of quantized charges is extremal. The spacetime is of the Reissner-Nordstrom

Hideaki Aoyama, Toshiyuki Harano, Masatoshi Sato, Shinya Wada

Microscopic tests of the exact results are performed in N=2 SU(2) supersymmetric QCD. We construct the multi-instanton solution in N=2 supersymmetric QCD and calculate the two-instanton contribution ${\cal F}_2$ to the prepotential ${\cal F}$ explicitly. For $N_f=1,2$, instanton calculus agrees with the prediction of the exact results, however, for $N_f=3$,

Piotr Kochanski, Krzysztof Wodkiewicz

The concept of intrinsic and operational observables in quantum mechanics is introduced. It is argued that, in any realistic description of a quantum measurement that includes a detecting device, it is possible to construct from the statistics of the recorded raw data a set of operational quantities that correspond to the intrinsic quantum mechanical observa

M. Baldo, G. F. Burgio, I. Bombaci

We calculate static properties of non-rotating neutron stars (NS&#39;s) using a microscopic equation of state (EOS) for asymmetric nuclear matter. The EOS is computed in the framework of the Brueckner--Bethe--Goldstone many--body theory. We introduce three-body forces in order to reproduce the correct saturation point of nuclear matter. A microscopic well be

Axel Gross, Matthias Scheffler

The influence of molecular vibrations on dissociative adsorption is studied by six-dimensional quantum dynamical calculations. For the system H_2 at Pd(100), which possesses non-activated pathways, it is shown that large vibrational effects exist and that they are not due to a strongly curved reaction path and a late dissociation-hindering minimum barrier, a

N. Moll, A. Kley, E. Pehlke, M. Scheffler

Surface energies for different GaAs surface orientations have been calculated as a function of the chemical potential. We use an energy density formalism within the first-principles pseudopotential density-functional approach. The equilibrium crystal shape (ECS) has been derived from the surface energies for the (110), (100), (111), and (-1-1-1) orientations

M. V. Ganduglia-Pirovano, V. Natoli, M. H. Cohen, J. Kudrnovsky

We have extended the validity of the correlation between the surface 3d-core-level shift (SCLS) and the surface d band shift (SDBS) to the entire 4d transition metal series and to the neighboring elements Sr and Ag via accurate first-principles calculations. We find that the correlation is quasilinear and robust with respect to the differencies both between

Axel Gross, Matthias Scheffler

Among other things (e.g. steering and steric effects in dissociative adsorption) we had predicted that the initial sticking probability of H_2 molecules impinging at clean Pd(100) exhibits oscillations, reflecting the quantum nature of the scattering process. In the preceding comment Rettner and Auerbach (RA) analyze experimental results and conclude that th

J. S. Prakash, H. S. Sharatchandra

We develop a simple computational tool for $SU(3)$ analogous to Bargmann&#39;s calculus for $SU(2)$. Crucial new inputs are, (i) explicit representation of the Gelfand-Zetlin basis in terms of polynomials in four variables and positive or negative integral powers of a fifth variable (ii) an auxiliary Gaussian measure with respect to which the Gelfand-Zetlin

Amir Masoud Ghezelbash

We consider the standard vector gauging of Lorentz group $ SO(3,1) $ WZW model by its non-semisimple null Euclidean subgroup in two dimensions $ E(2) $. The resultant effective action of the theory is seen to describe a one dimensional bosonic field in the presence of external charge that we interpret it as a Liouville field. Gauging a boosted $ SO(3) $ subg

Bergfinnur Durhuus, Thordur Jonsson

We study an ensemble of branched polymers which are embedded on other branched polymers. This is a toy model which allows us to study explicitly the reaction of a statistical system on an underlying geometrical structure, a problem of interest in the study of the interaction of matter and quantized gravity. We find a phase transition at which the embedded po

A. G. Ushveridze

The quantum mechanical concept of quasi-exact solvability is based on the idea of partial algebraizability of spectral problem. This concept is not directly extendable to the systems with infinite number of degrees of freedom. For such systems a new concept based on the partial Bethe Ansatz solvability is proposed. In present paper we demonstrate the constru

N. A. Saulina, M. V. Terentiev, K. N. Zyablyuk

Equations of motion and the lagrangian are derived explicitely for Dual D=10, N=1 Supergravity considered as a field theory limit of a Fivebrane. It is used the mass-shell solution of Heterotic String Bianchi Identites obtained in the 2-dimensional $σ$-model two-loop approximation and in the tree-level Heterotic String approximation. As a result the Dual Sup

W. de Boer, A. Dabelstein, W. Hollik, W. Moesle

The Minimal supersymmetric extension of the Standard Model (MSSM) with light stops, charginos or pseudoscalar Higgs bosons has been suggested as an explanation of the too high value of the branching ratio of the Z0 boson into b quarks (Rb anomaly). A program including all radiative corrections to the MSSM at the same level as the radiative corrections to the

Joao M. Soares

Relations between the form factors that parametrize the hadronic matrix elements, in spectator decays of heavy mesons, have been derived by Stech within the constituent quark model. In here, we examine these relations using a slightly modified description of the meson states. We find new and very general relations for some of the form factors. For the other

R. S. Willey

We show that MS bar perturbation theory develops tachyonic singularities for some value of the dimensional regularization scale mu unless the physical Higgs mass exceeds some (cutoff dependent) minimum value.

Michael I. Eides, Howard Grotch

Several new corrections of order $mα^6$ to the energy levels of $S$ states in helium are obtained from radiative corrections to the Breit potential and from the polarization insertions in the two photon exchange graphs. While individual gauge invariant contributions are comparable to current experimental errors, the sum of these corrections is an order of ma

P. Kroll

The present status of the diquark model for exclusive reactions at moderately large momentum transfer is reviewed. That model is a variant of the Brodsky-Lepage approach in which diquarks are considered as quasi-elementary constituents of baryons. Recent applications of the diquark model, relevant to high energy physics with electromagnetic probes, are discu

R. Casalbuoni, S. De Curtis, D. Dominici, M. Grazzini

We present a renormalizable model of electroweak interactions containing an extra $SU(2)&#39;_L\otimes SU(2)&#39;_R$ symmetry. The masses of the corresponding gauge bosons and of the associated Higgs particles can be made heavy by tuning a convenient vacuum expectation value. According to the way in which the heavy mass limit is taken we obtain a previously

G. V. Dass, K. V . L. Sarma

In order to detect the possible presence of $ΔB = - ΔQ$ amplitudes in neutral $B$ meson decays, we consider the measurement of decay time asymmetries involving like-sign dilepton events at the $B$ factories.

M. Kawasaki, N. Sugiyama, T. Yanagida

The $eeγγ+\rlap/E_T$ event observed by the CDF at Fermilab is naturally explained by dynamically supersymmetry breaking models and suggests the presence of the light gravitino which can be a warm dark matter. We consider large scale structure of the universe in the worm dark matter model and find that the warm dark matter plays almost the same role in the fo

Paolo Cea, Leonardo Cosmai

We analyze the problem of the Nielsen-Olesen unstable modes in the $SU(2)$ lattice gauge theory by means of a recently introduced gauge-invariant effective action. We perform numerical simulations in the case of a constant Abelian chromomagnetic field. We find that for lattice sizes above a certain critical length the density of effective action shows a beha

I. Dasgupta, A. R. Levi, V. Lubicz, C. Rebbi

We implement lattice QCD using the Fortran 90 language. We have designed machine independent modules that define fields (gauge, fermions, scalars, etc...) and have defined overloaded operators for all possible operations between fields, matrices and numbers. With these modules it is very simple to write QCD programs. We have also created a useful compression

R. B. Mann

I discuss a method for obtaining the one-loop quantum corrections to the tree-level entropy for a charged Kerr black hole. Divergences which appear can be removed by renormalization of couplings in the tree-level gravitational action in a manner similar to that for a static black hole.

Ivar Martin, Yi Wan, Philip Phillips

We study here the role randomly-placed non-magnetic scatterers play on the Kondo effect. We show that spin relaxation effects (with time $τ_s^o$)in the vertex corrections to the Kondo self-energy lead to an exact cancellation of the singular temperature dependence arising from the diffusion poles. For a thin film of thickness $L$ and a mean-free path $\ell$,

S. F. Burlatsky, G. Oshanin, M. Morea, W. P. Reinhardt

We study the dynamics of a tracer particle subject to a constant driving force $E$ in a one-dimensional lattice gas of hard-core particles whose transition rates are symmetric. We show that the mean displacement of the driven tracer grows in time, $t$, as $ \sqrt{αt}$, rather than the linear time dependence found for driven diffusion in the bath of non-inter

Andreas Rudinger, Clement Sire

The multifractal properties of the electronic spectrum of a general quasiperiodic chain are studied in first order in the quasiperiodic potential strength. Analytical expressions for the generalized dimensions are found and are in good agreement with numerical simulations. These first order results do not depend on the irrational incommensurability.

M. Batsch, L. Schweitzer, I. Kh. Zharekeshev, B. Kramer

We report a novel scale-independent, Aharonov-Bohm flux controlled crossover from critical orthogonal to critical unitary statistics at the disorder induced metal insulator transition. Our numerical investigations show that at the critical point the level statistics are definitely distinct and determined by fundamental symmetries. The latter is similar to th

Samuele Bottani, Bertrand Delamotte

We reexamine the dynamics of the Olami, Feder and Christensen (OFC) model. We show that, depending on the dissipation, it exhibits two different behaviors and that it can or cannot show self - organized - criticality (SOC) and/or synchronization. We also show that while the Feder and Feder model perturbed by a stochastic noise is SOC and has the same exponen

Zong-Chao Yan, James F. Babb, A. Dalgarno, G. W. F. Drake

The dispersion coefficients $C_6$, $C_8$, and $C_{10}$ for the interactions between H, He, and Li are calculated using variational wave functions in Hylleraas basis sets with multiple exponential scale factors. With these highly correlated wave functions, significant improvements are made upon previous calculations and our results provide definitive values f

Lyle Ford, David Band

Many gamma-ray burst counterpart searches are being conducted in the optical-UV band. To both predict detectability and understand the meaning of any detections or upper limits, we extrapolate gamma-ray spectra from 54 bright gamma-ray bursts to optical-UV energies. We assume optical emission is concurrent with gamma-ray emission and do not consider quiescen

Y. -N. Chin, C. Henkel, T. J. Millar, J. B. Whiteoak

The first definite discoveries of extragalactic deuterium are reported. DCO$^+$ has been detected in three and DCN has been measured in one star-forming region of the Large Magellanic Cloud (LMC). While the HCO$^+$/DCO$^+$ abundance ratios are found to be 19 $\pm$ 3, 24 $\pm$ 4, and 67 $\pm$ 18 for N113, N44BC and N159HW, respectively, a HCN/DCN abundance ra

David S. Davis, Raymond E. White

We determine X-ray temperatures and abundances for elliptical galaxies drawn from a complete, optically selected sample. The optical magnitude-limited sample consists of 43 galaxies, complete to a (corrected) B magnitude of m_B^o=11.36. Of these, 30 have enough X-ray spectral counts to allow temperature determinations. We find that the temperatures of the X-

A. Comastri, T. Di Girolamo, G. Setti

The contribution of discrete sources to the gamma--ray background is modeled. Flat spectrum radio quasars are known to make a substantial contribution to the hard (E > 100 MeV) background. The so called ``MeV bump&#34;, however, cannot be accounted for in terms of known classes of sources even taking into account the newly discovered class of objects with a

Hyesung Kang, T. W. Jones

We report simulations of diffusive particle acceleration in oblique magnetohydrodynamical (MHD) shocks. These calculations are based on extension to oblique shocks of a numerical model for ``thermal leakage&#39;&#39; injection of particles at low energy into the cosmic-ray population. That technique, incorporated into a fully dynamical diffusion-convection f

Paolo Aluffi

We prove a simple formula for MacPherson&#39;s Chern class of hypersurfaces in nonsingular varieties. The result highlights the relation between MacPherson&#39;s class and other definitions of homology Chern classes of singular varieties, such as Mather&#39;s Chern class and a class introduced by W. Fulton.