August 1994 arXiv papers — page 7

A. Boresch, K. Landsteiner, W. Lerche, A. Sevrin

In any string theory there is a hidden, twisted superconformal symmetry algebra, part of which is made up by the BRST current and the anti-ghost. We investigate how this algebra can be systematically constructed for strings with $N\!-\!2$ supersymmetries, via quantum Hamiltonian reduction of the Lie superalgebras $osp(N|2)$. The motivation is to understand h

M. Yu. Kalmykov, P. I. Pronin, K. V. Stepanyantz

We investigate the influence of the projective invariance on the renormalization properties of the theory. One-loop counterterms are calculated in the most general case of interaction of gravity with scalar field.

P. Aschieri, L. Castellani

A review of the multiparametric linear quantum group GL_qr(N), its real forms, its dual algebra U(gl_qr(N)) and its bicovariant differential calculus is given in the first part of the paper. We then construct the (multiparametric) linear inhomogeneous quantum group IGL_qr(N) as a projection from GL_qr(N+1), or equivalently, as a quotient of GL_qr(N+1) with r

O. Moritsch, M. Schweda, T. Sommer

The BRST transformations for the Yang-Mills gauge fields in the presence of gravity with torsion are discussed by using the so-called Maurer-Cartan horizontality conditions. With the help of an operator $\d$ which allows to decompose the exterior spacetime derivative as a BRST commutator we solve the Wess-Zumino consistency condition corresponding to invaria

V. Dimitrov, J. Engel, S. Pittel

We use a "hybrid" method, mixing variationally-determined triaxial nuclear Slater determinants, to calculate the response of Ge73 to hypothetical dark-matter particles such as neutralinos. The method is a hybrid in that rotational invariance is approximately restored prior to variation and then fully restored before the mixing of intrinsic states. We discuss

A. H. Nueller

{\narrower\smallskip High Energy onium-onium scattering is calculated as a function of impact parameter in the one and two pomeron exchange approximation. Difficulties with using the multiple scattering series to unitarize single pomeron exchange at high energy are noted. An operator formalsim which sums all numbers of pomeron exchange is given. A toy model

T. V. Duong, Ernest Ma

In two recently proposed supersymmetric extended electroweak gauge models, the reduced Higgs sector at the 100-GeV energy scale consists of only two doublets, but they have quartic scalar couplings different from those of the minimal supersymmetric standard model. In the SU(2) X SU(2) X U(1) model, there is an absolute upper bound of about 145 GeV on the mas

Chao-Qiang Geng, Paul Turcotte, Wei-Shu Hou

Using the recent CLEO measurement of $Br(b\to s γ)$, we find that the branching ratio of $b\to s g$ cannot be larger than $10\%$ in two Higgs doublet models. The small experimental value of $Br(b\to e\barνX)$ can no longer be explained by charged Higgs boson effects.

Mark Hindmarsh

This work is based on a paper with Margaret James, to appear in Phys Rev D. In it we showed that the dipole moment of the sphaleron has its origin in two components: a ring of electric current circulating around the edge of the sphaleron; and also two regions of opposite magnetic charge above and below the ring. This magnetic charge has a partly topological

Vittorio Del Duca, Carl R. Schmidt

In this talk we examine the azimuthal angle decorrelation in dijet production at large rapidity intervals at the Tevatron as a possible signature of the BFKL evolution.

Irinel Caprini

We derive optimal upper and lower bounds on the slope of the Isgur-Wise function at the zero recoil point in terms of the sum of the $ΥB\bar{B}$ couplings, estimated recently from a $QCD$ Spectral Sum Rule ($QSSR$). The problem is solved by means of a duality theorem in functional optimization. Optimal correlations between the slope and the convexity paramet

Ray L. Renken, Simon M. Catterall, John B. Kogut

Recently a block spin renormalization group approach was proposed for the dynamical triangulation formulation of two-dimensional quantum gravity. We use this approach to examine non-perturbatively a particular class of higher derivative actions for pure gravity.

E. Calzetta, C. El Hasi

Inflationary cosmologies, regarded as dynamical systems, have rather simple asymptotic behavior, insofar as the cosmic baldness principle holds. Nevertheless, in the early stages of an inflationary process, the dynamical behavior may be very complex. In this paper, we show how even a simple inflationary scenario, based on Linde's ``chaotic inflation'

Neil Cornish

The analog of the Schwarzschild metric is explored in the context of Non-Singular Gravity. Analytic results are developed describing redshifts, curvatures and topological features of the spacetime. All curvatures and redshifts are finite so there are no Black Holes, no singularities and no Hawking radiation.

M. Vekic, J. W. Cannon, D. J. Scalapino, R. T. Scalettar

We study the two-dimensional periodic Anderson model at half-filling using quantum Monte Carlo (QMC) techniques. The ground state undergoes a magnetic order-disorder transition as a function of the effective exchange coupling between the conduction and localized bands. Low-lying spin and charge excitations are determined using the maximum entropy method to a

Frank Gaitan

A microscopic analysis of the non-dissipative force ${\bf F}_{nd}$ acting on a line vortex in a type-II superconductor at $T=0$ is given. We first examine the Berry phase induced in the true superconducting ground state by movement of the vortex and show how this induces a Wess-Zumino term in the hydrodynamic action $S_{hyd}$ of the superconducting condensat

Hirokazu Tsunetsugu, Matthias Troyer, T. M. Rice

The energies of singlet stripe phases in which a plane is broken up into spin liquid ladders by lines of holes, is examined. If the holes were static then patterns containing spin liquids with a finite spin gap are favored. The case of dynamic holes is treated by assembling t-J ladders oriented perpendicular to the stripes. For a wide region around $J/t \app

M. Reigrotzki, H. Tsunetsugu, T. M. Rice

The properties of antiferromagnetic Heisenberg $S=\frac{1}{2}$ ladders with 2, 3, and 4 chains are expanded in the ratio of the intra- and interchain coupling constants. A simple mapping procedure is introduced to relate the 4 and 2-chain ladders which holds down to moderate values of the expansion parameters. A second order calculation of the spin gap to th

D. Dhar, P. Ruelle, S. Sen, D. -N. Verma

The abelian sandpile models feature a finite abelian group $G$ generated by the operators corresponding to particle addition at various sites. We study the canonical decomposition of $G$ as a product of cyclic groups $G = Z_{d_1} \times Z_{d_2} \times Z_{d_3} >... \times Z_{d_g}$ where $g$ is the least number of generators of $G$, and $d_i$ is a multiple of

D. N. Aristov, A. G. Yashenkin

We examine the NMR experimental data for the normal state of YBa$_2$Cu$_3$O$_{7-δ}$ within the Fermi-liquid approach. We show that the observed temperature dependence of the Knight shift and $^{17}$O ($^{89}$Y) relaxation rate in ``underdoped'' ( $T_c=60\,$K ) compound can be interpreted as resulting from a peak in the density of states near the Ferm

D. Dhar, P. Ruelle, S. Sen, D. -N. Verma

The abelian sandpile models feature a finite abelian group G generated by the operators corresponding to particle addition at various sites. We study the canonical decomposition of G as a product of cyclic groups G = Z_{d_1} X Z_{d_2} X Z_{d_3}...X Z_{d_g}, where g is the least number of generators of G, and d_i is a multiple of d_{i+1}. The structure of G i

Lawrence M. Chernin, Douglas Scott

We present sensitive upper limits on the 90 GHz flux of known radio and infrared sources in regions associated with possible cosmic microwave background fluctuations at 0.5--1 degree scales. Specifically we look at the MAX GUM region and the region of strongest fluctuation in the MSAM scan. None of the known sources can account for the levels of anisotropy s

E. F. Borra

This paper considers the hypothesis that BL Lacertae objects (BLLs) are the beamed remnants of Quasi Stellar Objects. The hypothesis explains why BLLs do not undergo the strong evolution seen in other active galactic nuclei since it naturally predicts that the space density of BLLs should increase with cosmic time, as shown by recent observations. Numerical

F. Lucchin, S. Matarrese, A. Messina, L. Moscardini

We analyse the large--scale velocity field obtained by N--body simulations of cold dark matter (CDM) models with non--Gaussian primordial density fluctuations, considering models with both positive and negative primordial skewness in the density fluctuation distribution. We study the velocity probability distribution and calculate the dependence of the bulk

Jaroslaw Kulpa, Slawomir Wycech

Validity of the coalescence model of exotic atom formation in the ion collisions is studied . An estimate is given for the rates of P state production in the electric fields of the colliding ions . Possibilities of quantum beat effects are indicated . The results may be of interest in the experimental search for pionium.

T. P. Devereaux, D. Einzel

A gauge invariant theory for electronic Raman scattering for superconductors with anisotropic pairing symmetry is analyzed in detail. It is shown that Raman scattering in anisotropic superconductors provides a wealth of polarization-dependent information which probes the detailed angular dependence of the superconducting ground state order parameter. The Ram

Craig D. Roberts

The electromagnetic pion form factor, $F_\pi(q^2)$, is calculated for spacelike-$q^2$ in impulse approximation using a confining quark propagator, $S$, and a dressed quark-photon vertex, $\Gamma_\mu$, obtained from realistic, nonperturbative Dyson-Schwinger equation studies. Good agreement with the available data is obtained for $F_\pi(q^2)$ and other pion o

A. Jadczyk

We propose a definite meaning to the concepts of "experiment", "measurement" and "event" in the event-enhanced formalism of quantum theory. A minimal piecewise deterministic process is given that can be used for a computer simulation of real time series of experiments on single quantum objects. As an example a generalized cloud chambe

B. Frois, P. J. Mulders

We summarize the discussion on the possibilities of doing inclusive and semi-inclusive deep inelastic scattering experiments at CEBAF with beam energy of the order of 10 GeV.

Nelson R. F. Braga, Ashok Das

We show that the BV (Batalin Vilkovisky) action, formulated with an extended BRST symmetry (including the shift symmetry), is also invariant under an extended anti-BRST transformation (where the antifields are the parameters of the transformation), when the gauge fixing Lagrangian is both BRST and anti-BRST invariant. We show that for a general gauge fixing

J. W. van Holten

We compare several parametrized analytic expressions for an arbitrary off-shell one-loop $n$-point function in scalar field theory in $D$-dimensional space-time, and show their equivalence both directly and through path-integral methods.

A. L. Larsen

String propagation is investigated in de Sitter and black hole backgrounds using both exact and approximative methods. The circular string evolution in de Sitter space is discussed in detail with respect to energy and pressure, mathematical solution and physical interpretation, multi-string solutions etc. We compare with the circular string evolution in the

Christoph Wetterich

We investigate the coupled system of gravity and a scalar with exponential potential. The energy momentum tensor of the scalar field induces a time-dependent cosmological ``constant''. This adjusts itself dynamically to become in the ``late'' universe (including today) proportional to the energy density of matter and radiation. Possible conse

Rainer Dick

It is shown that Weyl spinors in 4D Minkowski space are composed of primary fields of half-integer conformal weights. This yields representations of fermionic 2-point functions in terms of correlators of primary fields with a factorized transformation behavior under the Lorentz group. I employ this observation to determine the general structure of the corres

Juan Garcia-Bellido, Andrei Linde

We describe several different regimes which are possible in inflationary cosmology. The simplest one is inflation without self-reproduction of the universe. In this scenario the universe is not stationary. The second regime, which exists in a broad class of inflationary models, is eternal inflation with the self-reproduction of inflationary domains. In this

A. Jadczyk

We propose a definite meaning to the concepts of "experiment", "measurement" and "event" in the event-enhanced formalism of quantum theory. A minimal piecewise deterministic process is given that can be used for a computer simulation of real time series of experiments on single quantum objects. As an example a generalized cloud chambe

Ernest Ma

A new supersymmetric gauge model is proposed with particle content chosen only from the 27 and 27* representations of E_6. The gauge symmetry SU(3) X SU(2)_L X SU(2)_R X U(1) is realized at the TeV energy scale and the gauge couplings converge to a single value at around 10^{16} GeV. A discrete Z_4 X Z_2 symmetry leads to a generalized definition of lepton n

Xuemin Jin

Sum rules for the variation of finite-density spectral density of vector channel with baryon density are derived based on dispersion relations and the operator product expansion. These sum rules may serve as constraints on the phenomenological models for the finite-density spectral densities used in the approaches motivated from QCD. Applying these sum rules

I. I. Bigi

A list is given of those open questions concerning the dynamics of charm decays where there exists a strong need for an answer. Such a need is based on lessons to be learnt about QCD -- either in their own right or for a better understanding of $B$ physics -- or on searches for New Physics with a small background from the Standard Model. The major items on t

P. I. Krastev, S. T. Petcov

Solar model independent tests of the vacuum oscillation and MSW solutions of the solar neutrino problem are considered. Detailed predictions for time (seasonal) variations of the signals in the future solar neutrino detectors (SNO, Super Kamiokande, BOREXINO, HELLAZ), if solar neutrinos take part in vacuum oscillations, are given. Results on the distortions

E. Pallante

We derive the S parameter of the electroweak radiative corrections in a scaled-QCD technicolour and using a Nambu-Jona Lasinio model for hadronic low energy interactions. In this framework deviations from low energy QCD can be quantitatively deduced. We induce explicit chiral symmetry breaking in the NJL model through the current-quarks mass term. It is show

E. Pallante

The hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon is parametrized by using the quark-resonance model formulated in \cite{QR}. In this context a recent prediction obtained within the ENJL model \cite{RAF} can be affected by two additional contributions: the next to leading corrections in the inverse cutoff expansion an

Diego J. Castano, Stephen P. Martin

Many extensions of the minimal supersymmetric standard model contain superfields for quarks which are singlets under weak isospin with electric charge -1/3. We explore the possibility that such isosinglet quarks have low or intermediate scale masses, but do not mediate rapid proton decay because of a discrete symmetry. By imposing the discrete gauge anomaly

G. C. Branco, G. C. Cho, Y. Kizukuri, N. Oshimo

We show that in the supersymmetric standard model (SSM) box diagrams mediated by charginos and up-type squarks may give large contributions to $\BB$ and $\KK$ mixings. This is due to the fact that a heavy top quark mass allows large mass differences among the up-type squarks, which leads to a less efficient cancellation among the different squark diagrams. I

James D. Wells, Chris Kolda, G. L. Kane

Assuming that the actual values of the top quark mass at FNAL and of the ratio of partial widths Z->bb/Z->hadrons at LEP are within their current one-sigma reported ranges, we present a No-Lose Theorem for superpartner searches at LEP II and an upgraded Tevatron. We impose only two theoretical assumptions: the Lagrangian is that of the Minimal Supersymmetric

Jeffrey E. Mandula, Michael C. Ogilvie

A preliminary computation of the Isgur-Wise universal form factor using a lattice formulation of the Heavy Quark Effective Theory (HQET) is described and compared with the recent data from ARGUS and CLEO on B -> D*lv decay.

M. Hasenbusch, M. Marcu, K. Pinn

We study the expansion of the surface thickness in the 2-dimensional lattice Sine Gordon model in powers of the fugacity z. Using the expansion to order z**2, we derive lines of constant physics in the rough phase. We describe and test a VMR cluster algorithm for the Monte Carlo simulation of the model. The algorithm shows nearly no critical slowing down. We

J. Schirmer

It was noted recently that the ADM-diffeomorphism-constraint does not generate all observed symmetries for several Bianchi-models. We will suggest not to use the ADM-constraint restricted to homogeneous variables, but some equivalent which is derived from a restricted action principle. This will generate all homogeneity preserving diffeomorphisms, which will

S. Guruswamy, S. G. Rajeev, P. Vitale

This talk is based on a recent paper$^{1}$ of ours. In an attempt to understand three-dimensional conformal field theories, we study in detail one such example --the large $N$ limit of the $O(N)$ non-linear sigma model at its non-trivial fixed point -- in the zeta function regularization. We study this on various three-dimensional manifolds of constant curva

Yan V. Fyodorov

The explicit analytical expression for the distribution function of parametric derivatives of energy levels ("level velocities") with respect to a random change of scattering potential is derived for the chaotic quantum systems belonging to the quasi 1D universality class (quantum kicked rotator, "domino" billiard, disordered wire, etc.).

Chetan Nayak, Frank Wilczek

We expand upon on an earlier renormalization group analysis of a non-Fermi liquid fixed point that plausibly govers the two dimensional electron liquid in a magnetic field near filling fraction $ν=1/2$. We give a more complete description of our somewhat unorthodox renormalization group transformation by relating both our field-theoretic approach to a direct

Takahiro Fukui, Norio Kawakami

The idea of fractional exclusion statistics proposed by Haldane is applied to systems with internal degrees of freedom, and its thermodynamics is examined. In case of one dimension, various bulk quantities calculated show that the critical behavior of such systems can be described by $c=1$ conformal field theories and conformal weights are completely charact

S. Flach

We use recent results that localized excitations in nonlinear Hamiltonian lattices can be viewed and described as multiple-frequency excitations. Their dynamics in phase space takes place on tori of corresponding dimension. For a one-dimensional Hamiltonian lattice with nearest neighbour interaction we transform the problem of solving the coupled differentia

S. Flach

We use recent results that localized excitations in nonlinear Hamiltonian lattices can be viewed and described as multiple-frequency excitations. Their dynamics in phase space takes place on tori of corresponding dimension. For a one-dimensional Hamiltonian lattice with nearest neighbour interaction we transform the problem of solving the coupled differentia

Keith Briggs

I discuss the universal aspects of scaling in period-doubling sequences in families of maps of the real line possessing non-integer degree. I show that the scaling behaviour in both the orbital and parameter spaces is governed by the same sequence of eigenvalues of the linearized renormalization operator. These eigenvalues are smooth functions of the degree

Adrian L. Melott, Jennifer L. Pauls

In recent years there has been a developing realization that the interesting large--scale structure of voids, ``pancakes", and filaments in the Universe is a consequence of the efficacy of an approximation scheme for cosmological gravitation clustering proposal by Zel'dovich in 1970. However, this scheme was only supposed to apply to smoothed initial

James E. Lidsey, I. Waga

The andante regime of scalar field dynamics in the chaotic inflationary Universe is defined as the epoch when the field is rolling moderately slowly down its interaction potential, but at such a rate that first-order corrections to the slow-roll approximation become important. These conditions should apply towards the end of inflation as the field approaches

Andrew R. Liddle, Paul Parsons, John D. Barrow

The meaning of the inflationary slow-roll approximation is formalised. Comparisons are made between an approach based on the Hamilton-Jacobi equations, governing the evolution of the Hubble parameter, and the usual scenario based on the evolution of the potential energy density. The vital role of the inflationary attractor solution is emphasised, and some of

Louis Martinet

After a recall of fundamental concepts used in galactic dynamics, we review observational facts as well as results of orbit theory and numerical simulations which suggest long-term evolution of galaxies. Dynamical interactions between galaxy constituents (bulges, disks, bars, haloes, dark matter) are discussed and effects of external perturbations on interna

W. Bednarek, J. G. Kirk

We analyse the propagation of particles in the narrow funnel of a thick accretion disk. It is assumed that: (1) the funnel walls emit black body radiation with temperature decreasing outwards; (2) the magnetic and electric fields are longitudinal in the funnel. Such a scenario is consistent with models in which a large potential drop is induced by a rotating

Lothar Goettsche, Daniel Huybrechts

We show that the Hodge numbers of the moduli space of stable rank two sheaves with primitive determinant on a K3 surface coincide with the Hodge numbers of an appropriate Hilbert scheme of points on the K3 surface. The precise result is: Theorem: Let $X$ be a K3 surface, $L$ a primitive big and nef line bundle and $H$ a generic polarization. If the moduli sp

R. Klages, J. R. Dorfman

We consider chains of one-dimensional, piecewise linear, chaotic maps with uniform slope. We study the diffusive behaviour of an initially nonuniform distribution of points as a function of the slope of the map by solving Frobenius-Perron equation. For Markov partition values of the slope, we relate the diffusion coefficient to eigenvalues of the topological

Gregory J. Tawa, Lawrence R. Pratt

A dielectric solvation model is applied to the prediction of the equilibrium ionization of liquid water over a wide range of density and temperature with the objective of calibrating that model for the study of ionization in water of organic acids, {\it e.g.\/}, proteins and nucleic acids. The model includes an approximate description of the polarizability o

G. E. Brown, Mannque Rho

The chiral phase transition at high temperature and/or density is interpreted in terms of Georgi's vector limit. We discuss three cases as possible support for this scenario: Quark-number susceptibility, cool kaons in heavy-ion process and an instanton-molecule picture for chiral restoration. Both the notion of ``mended symmetry" and the Georgi vecto

Aharon Davidson, Eduard Gedalin

A finite-length magnetic vortex line solution is derived within the context of (4-dim) dilaton gravity. We approach the Bonnor metric at the Einstein-Maxwell limit, and encounter the "flux tube as (Euclidean) Kerr horizon" at the Kaluza-Klein level. Exclusively for string theory, the magnetic flux tube world-sheet exhibits a 2-dim black & white dihol

M. -C. Chu, S. Gardner, T. Matsui, R. Seki

An extended pion source, which can be temporarily created by a high energy nuclear collision, will also absorb and distort the outgoing pions. We discuss how this effect alters the interferometric pattern of the two-pion momentum correlation function. In particular, we show that the two-pion correlation function decreases rapidly when the opening angle betwe

Gerald A. Miller

Previous work on color transparency is reviewed briefly with an emphasis on aspects related to an upgrade of CEBAF.

J. Engel, C. R. Gould, V. Hnizdo

We derive a T-violating P-conserving optical potential for neutron-nucleus scattering, starting from a uniquely determined two-body $ρ$-exchange interaction with the same symmetry. We then obtain limits on the T-violating $ρ$-nucleon coupling $\overline{g}_ρ$ from neutron-transmission experiments in $^{165}$Ho. The limits may soon compete with those from mea

B. Schwesinger, F. G. Scholtz, H. B. Geyer

Hyperon pairs bound in deuteron like states are obtained within the SU(3) Skyrme model in agreement with general expectations from boson exchange models. The central binding from the flavor symmetry breaking terms increases with the strangeness contents of the interacting baryons whereas the kinetic non-linear $σ$-model term fixes the spin and isospin of the

A. Gangopadhyaya, A. Pagnamenta, U. Sukhatme

We describe the bound state and scattering properties of a quantum mechanical particle in a scalar $N$-prong potential. Such a study is of special interest since these situations are intermediate between one and two dimensions. The energy levels for the special case of $N$ identical prongs exhibit an alternating pattern of non-degeneracy and $(N-1)$ fold deg

E. Ramos, J. Roca

We prove that $\W_3$ is the gauge symmetry of the scale-invariant rigid particle, whose action is given by the integrated extrinsic curvature of its world line. This is achieved by showing that its equations of motion can be written in terms of the Boussinesq operator. The $\W_3$ generators $T$ and $W$ then appear respectively as functions of the induced wor

I. Pesando

We use the bilocal method to derive the large $N$ solution of the most general $QCD_2$.

Y. Brihaye, S. Giller, P. Kosinski

We construct representations of the enveloping algebra $U_q osp(2,2)$ in terms of finite difference operators and we discuss this result in the framework of quasi-exactly-solvable equations.

J. I. Latorre, P. Pascual, R. Tarrach

We unify all existing results on the change of the speed of low--energy photons due to modifications of the vacuum, finding that it is given by a universal constant times the quotient of the difference of energy densities between the usual and modified vacua over the mass of the electron to the fourth power. Whether photons move faster or slower than $c$ dep

Akira Fujii

Fisher's phenomenological renormalization method is used to calculate the mass gap and the correlation length of the $O(N)$ nonlinear $σ$ model on a semi-compact space $S^{1}\times {\bf R}^{2}$. This shows that the ultraviolet momentum cut-off does not conflict with the infrared cut-off along the $S^{1}$ direction. The mass gap on $S^{2}\times {\bf R}$ i

E. M. Henley, G. A. Miller

The semi-leptonic decays of $Σ^\pm$ offer a vehicle for observing charge symmetry-breaking. The effect is expected to be about 6\%, enhanced due to the replacement of two u quarks by d quarks. We propose that present experimental data be improved to search for this effect.

R. Arnowitt, Pran Nath

The expected event rates for ${\tilde Z_{1}}$ dark matter for a variety of dark matter detectors are studied over the full parameter space with tan $β\leq$ 20 for supergravity grand unified models. Radiative breaking constraints are implemented and effects of the heavy netural Higgs included as well as loop corrections to the neutral Higgs sector. The parame

Tony Gherghetta

Various prescriptions employed for regulating gauged Nambu--Jona-Lasinio type models such as the top-quark condensate model are discussed. The use of dimensional regularization maintains gauge invariance but destroys the quadratic divergence in the gap equation. If instead a simple ultraviolet momentum cutoff is used to regulate loop integrals, then gauge in

Anjan S. Joshipura, Marek Nowakowski

We analyze the spectrum and mixing among neutrinos in the minimal supersymmetric standard model with explicit breaking of R parity. It is shown that ({\em i}) the mixing among neutrinos is naturally large and ({\em ii}) the non zero neutrino mass is constrained to be $\leq 10^{-5}$ eV from arguments based on baryogenesis. Thus vacuum oscillations of neutrino

B. R. Webber

Power corrections to hadronic event shapes are estimated using a recently suggested relationship between perturbative and non-perturbative effects in QCD. The infrared cutoff dependence of perturbative calculations is related to non-perturbative contributions with the same dependence on the energy scale $Q$. Corrections proportional to $1/Q$ are predicted, i

W. Moedritsch, W. Kummer

Off-shell and relativistic bound-state corrections for the decay $t \to b+W$ are calculated to $O(\a_s^2)$ making full use of the Bethe-Salpeter formalism for weakly bound systems. Thus we are able to take into account all terms to that order in a systematic and straightforward manner. One of the previously not considered contributions cancels precisely gaug

W. Kummer, W. Moedritsch

Although individual levels of toponium will be unobservable, the top--anti--top system near threshold fulfills all requirements of a rigorous perturbation theory in QCD for weakly bound systems. Corresponding techniques from positronium may thus be transferred successfully to this case. After clarifying the effect of a non-zero width we calculate the $t\bar{

Giancarlo D'Ambrosio, Gino Isidori

We analyze $K \to ππγ$ decays in the framework of Chiral Perturbation Theory. We study the different Dalitz plot distributions, trying to find regions where o($p^6$) contributions could be more easily detected. To fulfill this program we compute all the the o($p^4$) loop and counterterm contributions, finding a substantial agreement with the existing calcula

Jihn E. Kim, Gye T. Park

We have performed a systematic analysis to compute the one-loop electroweak corrections to the Z->b b-bar vertex in terms of $\epsilon_b$ and $R_b$ in the context of the minimal $SU(5)$ and no-scale $SU(5)\times U(1)$ supergravity models. With the measured top mass, $m_t=174\pm 10^{+13}_{-12}$ $\GeV$ , recently announced by CDF, we use the latest LEP data on

Hiroshi Shiba, Tsuneo Suzuki

An effective monopole action for various extended monopoles is derived from vacuum configurations after abelian projection in the maximally abelian gauge in $SU(2)$ QCD. The action appears to be independent of the lattice volume. Moreover it seems to depend only on the physical lattice spacing of the renormalized lattice, not on $β$. Entropy dominance over e

R. Loll

We identify an explicit set of complete and independent Wilson loop invariants for 2+1 gravity on a three-manifold $M=\R\timesΣ^g$, with $Σ^g$ a compact oriented Riemann surface of arbitrary genus $g$. In the derivation we make use of a global cross section of the $PSU(1,1)$-principal bundle over Teichmüller space given in terms of Fenchel-Nielsen coordinate

F. Englert

Quantum physics at scales large compared to the Planck scale is described in the framework of classical space-time geometries. A criterion for selecting these backgrounds out of quantized gravity is proposed. It leads to an instability of the black-hole geometry, as experienced by motion across the horizon, against emission of Hawking quanta. A phenomenologi

Daniel S. Fisher, Aris L. Moustakas

It has been conjectured that an impurity with charge Z greater or equal to 2 can be localized due to its interaction with electrons in a metal. The simplest case is an impurity free to move between only two sites, which interacts locally with s-wave electrons. For Z greater or equal to 2 the hopping of the impurity is formally irrelevant and this has been ar

W. H"ubner, K. H. Bennemann, K. Böhmer

We show that the nonlinear optical response reflects sensitively the electronic structure of transition-metal surfaces and interfaces. $d$ and $s$ electrons may contribute rather differently to the second harmonic generation (SHG) signal. This results from the different sensitivity of $d$ and $s$ electrons to surface and symmetry changes. Consequently, SHG f

Benjamin P. Lee, John Cardy

We study reaction zones in three different versions of the A+B->0 system. For a steady state formed by opposing currents of A and B particles we derive scaling behavior via renormalization group analysis. By use of a previously developed analogy, these results are extended to the time-dependent case of an initially segregated system. We also consider an init

T. Nakajima, H. Aoki

The double fractional quantum Hall system of spin 1/2 electrons is numerically studied to predict that there exists a novel spin-unpolarized quantum liquid specific to the multi-species system, which exemplifies a link between the spin state and the inter-layer electron correlation. Even when the ground state is spin-polarized, the lowest charge-excitation m

T. R. Kirkpatrick, D. Belitz

The Anderson-Mott transition of disordered interacting electrons is shown to share many physical and technical features with classical random-field systems. A renormalization group study of an order parameter field theory for the Anderson-Mott transition shows that random-field terms appear at one-loop order. They lead to an upper critical dimension $d_{c}^{

P. J. Forrester

The ground state single particle Green's function describing hole propagation is calculated exactly for the $1/r^2$ quantum many body system at integer coupling. The result is in agreement with a recent conjecture of Haldane.

Afzal Ballim, Graham Russell

We present LHIP, a system for incremental grammar development using an extended DCG formalism. The system uses a robust island-based parsing method controlled by user-defined performance thresholds.

P. Duffy, L. O'C. Drury, H. J. Voelk

When a magnetised, thermal plasma containing a shock wave efficiently accelerates Cosmic Rays (CR) a reaction is exerted on the fluid structure. The simplest description of this process involves three conservation equations for the background fluid, with the CR pressure gradient included as an extra force, plus a hydrodynamic equation for the CR energy densi

Joseph L. Hora, William B. Latter

High-resolution near-infrared images and moderate resolution spectra were obtained of the bipolar nebulae M~2--9 and AFGL 2688. The ability to spatially and spectrally resolve the various components of the nebulae has proved to be important in determining their physical structure and characteristics. In M~2--9, the lobes are found to have a double-shell stru

D. A. Buote, J. C. Tsai

Using the simulation of Katz & White we have tested the viability of X-ray analysis for constraining the intrinsic shapes of clusters of galaxies considering the effects of both substructure and steep temperature gradients. We restrict analysis to aggregate cluster shapes on scales of $r\sim 1-2$ Mpc to reduce our sensitivity to core subclustering. For low r

David C. Dunbar, Paul S. Norridge

Techniques based upon the string organisation of amplitudes may be used to simplify field theory calculations. We apply these techniques to perturbative gravity and calculate all one-loop amplitudes for four-graviton scattering with arbitrary internal particle content. Decomposing the amplitudes into contributions arising from supersymmetric multiplets great

W. Kummer, W. Moedritsch

Recent evidence for the top mass in the region of 160 $GeV$ for the first time provides an opportunity to use the full power of relativistic quantum field theoretical methods, available also for weakly bound systems. Because of the large decay width $\G$ of the top quark individual energy-levels in "toponium" will be unobservable. However, the potent

D. V. Boulatov

We prove that the number of 3-dimensional simplicial complexes having the spherical topology grows exponentially as a function of a volume. It is suggested that the 3d simplicial quantum gravity has qualitatively the same phase structure as the O(n) matrix model in the dense phase.