August 1994 arXiv papers — page 3

Jochen Rau

A Brownian motion model is devised on the manifold of S-matrices, and applied to the calculation of conductance-conductance correlations and of the weak localization peak. The model predicts that (i) the correlation function in $B$ has the same shape and width as the weak localization peak; (ii) the functions behave as $\propto 1-{\cal O}(B^2)$, thus excludi

Marilyn A. Walker

Effective problem solving among multiple agents requires a better understanding of the role of communication in collaboration. In this paper we show that there are communicative strategies that greatly improve the performance of resource-bounded agents, but that these strategies are highly sensitive to the task requirements, situation parameters and agents&#

Hiyan Alshawi

This paper compares a qualitative reasoning model of translation with a quantitative statistical model. We consider these models within the context of two hypothetical speech translation systems, starting with a logic-based design and pointing out which of its characteristics are best preserved or eliminated in moving to the second, quantitative design. The

Hiyan Alshawi, David Carter

We present an automatic method for weighting the contributions of preference functions used in disambiguation. Initial scaling factors are derived as the solution to a least-squares minimization problem, and improvements are then made by hill-climbing. The method is applied to disambiguating sentences in the ATIS (Air Travel Information System) corpus, and t

Hsin-Hsi Chen, Yue-Shi Lee

This paper proposes an Approximate n-gram Markov Model for bag generation. Directed word association pairs with distances are used to approximate (n-1)-gram and n-gram training tables. This model has parameters of word association model, and merits of both word association model and Markov Model. The training knowledge for bag generation can be also applied

Matthias Bartelmann, Matthias Steinmetz, Achim Weiss

We construct a sample of numerical models for clusters of galaxies and employ these to investigate their capability of imaging background sources into long arcs. Emphasis is laid on the statistics of these arcs. We study cross sections for arc length and length-to-width ratio and optical depths for these arc properties, we examine the distribution of arc wid

K. Jedamzik, G. M. Fuller

We investigate the transport of baryon number across phase boundaries in a putative first order QCD-phase transition. Two independent phenomenological models are employed to estimate the baryon penetrability at the phase boundary: chromoelectric flux tube models; and an analogy to baryon-baryon coalescence in nuclear physics. Our analysis indicates that bary

K. Jedamzik

The formalism by Press and Schechter (PS) is often used to infer number densities of virialized objects of mass M (e.g. quasars, galaxies, clusters of galaxies, etc.) from a count of initially overdense regions in a Gaussian density perturbation field. We reanalyze the PS-formalism by explicitly counting underdense regions which are embedded within overdense

Caryn Werner

We construct a surface of general type with invariants \( χ= K^2 = 1 \) and torsion group \( \Bbb{Z}/{2} \). We use a double plane construction by finding a plane curve with certain singularities, resolving these, and taking the double cover branched along the resulting smooth curve.

S. L'vovsky

In his preprint ``Differential-Geometric Characterizations of Complete Intersections'' (alg-geom/9407002), J.M.Landsberg introduces an elementary characterization of complete intersections. The proof of this criterion uses the method of moving frames. The aim of this note is to present an elementary proof of Landsberg's criterion that is valid ov

Donald Spector

I give an interpretation of the fundamental theorem of algebra based on supersymmetry and the Witten index. The argument gives a physical explanation of why a real polynomial of degree $n$ need not have $n$ real zeroes, while a complex polynomial of degree $n$ must have $n$ complex zeroes. This paper also addresses in a general and model-independent way the

B. Normand, H. Kohno, H. Fukuyama

We consider the effects on phonon dynamics of spin-lattice coupling within the slave-boson mean-field treatment of the extended $t$-$J$ model. With no additional assumptions the theory is found to give a semi-quantitative account of the frequency and linewidth anomalies observed by Raman and neutron scattering for the 340$cm^{-1}$ $B_{1g}$ phonon mode in $YB

Anne Schilling, Peter van Nieuwenhuizen

We reformulate the proof of the renormalization of a spontaneously broken gauge theory by multiplicatively renormalizing the vacuum expectation value of the Higgs field in the $SU(2)$~Higgs model.

D. Kharzeev, H. Satz

We show that in a hot hadron gas, chiral symmetry restoration and deconfinement lead to a strong suppression of dilepton production by pion annihilation in the continuum above the $ρ-ω-ϕ$ peak. The suppression due to deconfinement persists also for annihilation reactions involving heavier mesons.

S. D. Bass

I discuss the chiral dynamics of Gribov's theory of confinement. At a critical coupling $α_s^c$ the light quark vacuum undergoes a series of phase transitions which should be taken into account in the application of chiral perturbation theory. The Gribov theory offers a simple explanation of the value of the pion nucleon sigma term without need to invoke

Chong-Shong Gao, Jing-Liang Hu, Cai-Dian Lu, Zhao-Ming Qiu

We give a more complete calculation of $b \to sγ$ decay, including leading log QCD corrections from $m_{top}$ to $M_W$ in addition to corrections from $M_{W}$ to $m_b$. We have included the full set of dimension-6 operators and corrected numerical mistakes of anomalous dimensions in a previous paper\cite{Cho}. Comparing with the calculations without QCD runn

J. M. Haeuser, W. Cassing, A. Peter, M. H. Thoma

Using the cluster expansions for n-point Green functions we derive a closed set of dynamical equations of motion for connected equal-time Green functions by neglecting all connected functions higher than $4^{th}$ order for the $λΦ^4$-theory in $1+1$ dimensions. We apply the equations to the investigation of spontaneous ground state symmetry breaking, i.e. to

Motowo Yamanobe, Sumio Ishikawa, Yasuhiro Iwama, Tadashi Miyazaki

The Kalb-Ramond action for an interacting string is generalized to the case of a high-dimensional object (p-brane). The interaction is found to be mediated by a gauge boson of a completely antisymmetric tensor of rank $p+1$.

Toshiya Kawai, Sung-Kil Yang

We discuss duality and mirror symmetry phenomena of Landau-Ginzburg orbifolds considering their elliptic genera. Under the duality (or mirror) transform performed by orbifoldizing the Landau-Ginzburg model via some discrete group of the superpotential we observe that the roles of the untwisted and twisted sectors are exchanged. As explicit evidence detailed

Jan Ambjorn

I discuss recent progress in our understanding of two barriers in quantum gravity: $c > 1$ in the case of 2d quantum gravity and $D > 2$ in the case of Euclidean Einstein-Hilbert gravity formulated in space-time dimensions $D >2$.

A. Kovner, B. Rosenstein

We present a construction of fermionic operators in 3+1 dimensions in terms of bosonic fields in the framework of $QED_4$. The basic bosonic variables are the electric fields $E_i$ and their conjugate momenta $A_i$. Our construction generalizes the analogous constuction of fermionic operators in 2+1 dimensions. Loosely speaking, a fermionic operator is repre

Marcelo Carvalho, Luiz Claudio Queiroz Vilar, S. P. Sorella

The anomalies which occur in chiral WW_{3} gravity are characterized by solving the BRS consistency condition.

J. Ambjorn P. Bialas, Z. Burda, J. Jurkiewicz, B. Petersson

We study numerically the fractal structure of the intrinsic geometry of random surfaces coupled to matter fields with $c=1$. Using baby universe surgery it was possible to simulate randomly triangulated surfaces made of 260.000 triangles. Our results are consistent with the theoretical prediction $d_H = 2+\sqrt{2}$ for the intrinsic Hausdorff dimension.

S. Rouhani, A. Shariati

We show how Wigner's little group approach to the representation theory of Poincaré group may be generalized to the case of $κ$-deformed Poincaré group. We also derive the deformed Lorentz transformations of energy and momentum. We find that if the $κ$-deformed Poincaré group is adopted as the fundamental symmetry of nature, it results in deviations from

Bernice Durand, Tu Zhang

Starting from a general $\rm SU_2\times U_1$ invariant interaction Lagrangian ${\cal L}_{\rm int}$ with four-fermion interactions between top $t$ and bottom $b$ quarks and working in the bubble approximation, we get a single Higgs as a bound state of quark pairs by allowing both $\langle \bar tt\rangle$ and $\langle\bar bb\rangle$ to be nonzero and the $t$ a

Jiro KODAIRA, Tsuneo UEMATSU, Yoshiaki Yasui

We investigate the spin structure function $g_2 (x, Q^2 )$ in the framework of the operator product expansion and the renormalization group. The twist-3 operators appearing in QCD are examined and their relations are studied. It is noted that operators proportional to equation of motion appear in the operator mixing through renormalization, which can be stud

Jiro Kodaira, Satoshi Matsuda, Tsuneo Uematsu, Ken Sasaki

The QCD higher order effects to the polarized structure function $g_2(x, Q^2 )$ are reanalyzed for massive quarks in the context of the operator product expansion. We confirm that the lowest moment of $g_2 (x, Q^2 )$ which corresponds to the Burkhardt-Cottingham sum rule does {\sl not} suffer from radiative corrections in perturbative QCD.

Peter Cho, Sandip Trivedi, Mark Wise

Gluon fragmentation to $\chicJ(1P)$ followed by single photon emission represents the dominant source of prompt $J/\Psi$'s at the Tevatron for $p_\perp \gtap 6 \GeV$. Since fragmenting gluons are approximately transverse, their products are significantly polarized. We find that gluon fragmentation populates the helicity levels of $\chione$, $\chitwo$ and $J/

H. Dilger

We present an improvement of global Metropolis updating steps, the instanton hits, used in a hybrid Monte Carlo simulation of the two-flavor Schwinger model with staggered fermions. These hits are designed to change the topological sector of the gauge field. In order to match these hits to an unquenched simulation with pseudofermions, the approximate zero mo

Vladimir E. Kravtsov, Alexander D. Mirlin

Deviation of the level correlation function in a mesoscopic metallic sample from the Wigner--Dyson distribution is calculated by using a combination of the renormalization group and non-perturbative treatment. For given spatial dimension the found correction is determined by the sample conductance.

Georg Junker, Stephan Matthiesen

We study the classical properties of a supersymmetric system which is often used as a model for supersymmetric quantum mechanics. It is found that the classical dynamics of the bosonic as well as the fermionic degrees of freedom is fully described by a so--called quasi--classical solution. We also comment on the importance of this quasi--classical solution i

Francesco Tassone, Francesco Mauri, Roberto Car

We study the convergence and the stability of fictitious dynamical methods for electrons. First, we show that a particular damped second-order dynamics has a much faster rate of convergence to the ground-state than first-order steepest descent algorithms while retaining their numerical cost per time step. Our damped dynamics has efficiency comparable to that

P. Fendley, A. W. W. Ludwig, H. Saleur

The conductance for tunneling through a point contact between two $ν=1/3$ quantum Hall edges is described by a universal scaling function, which has recently been measured experimentally. We compute this universal function exactly, by using the thermodynamic Bethe ansatz and a Boltzmann equation.

A. Lazarian

Paramagnetic alignment of fractal suprathermally rotating grains is discussed. It is shown that if the concentration of H$_{2}$formation sites is low and resurfacing is active, fractal structure of grains enhances their alignment. Studying the influence of grain surface physics and chemistry on the alignment we found that there exist two critical values of g

M. Beneke

I discuss the interplay of infrared sensitivity in large order perturbative expansions with the presence of explicit nonperturbative corrections in the context of heavy quark expansions. The main focus is on inclusive decays and the status of the kinetic energy of the heavy quark. This talk summarizes work done with Braun and Zakharov.

Joshua Feinberg

We investigate static space dependent $\sigx=\lag\barψψ\rag$ saddle point configurations in the two dimensional Gross-Neveu model in the large N limit. We solve the saddle point condition for $\sigx$ explicitly by employing supersymmetric quantum mechanics and using simple properties of the diagonal resolvent of one dimensional Schrödinger operators rather t

J. Rosner

The standard model of electroweak interactions is reviewed, stressing the top quark's impact on precision tests and on determination of parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. Some opportunities for the study of CP violation in the decays of $b$-flavored mesons are mentioned, and the possibility of a new ``standard model'' secto

A. Mastichiadis J. G. Kirk

Adopting the hypothesis that the nonthermal emission of Active Galactic Nuclei (AGN) is primarily due to the acceleration of protons, we construct a simple model in which the interplay of acceleration and losses can be studied together with the formation of the emitted spectrum. The acceleration process is assumed to be of the first order Fermi type, and the

Michael Joyce, Tomislav Prokopec, Neil Turok

We describe a new effect which produces baryons at a first order electroweak phase transition. It operates when there is a CP-violating field present on propagating bubble walls. The novel aspect is that it involves a purely classical force, which alters the motion of particles across the wall and through diffusion creates a chiral asymmetry in front of the

Alan R. White

Three closely related topics are covered. The derivation of $O(g^4)$ Lipatov kernels in pure glue QCD. The significance of quarks for the physical Pomeron in QCD. The possible inter-relation of Pomeron dynamics with Electroweak symmetry breaking.

Toshio Aoyagi

We propose a network of oscillators to retrieve given patterns in which the oscillators keep a fixed phase relationship with one another. In this description, the phase and the amplitude of the oscillators can be regarded as the timing and the strength of the neuronal spikes, respectively. Using the amplitudes for encoding, we enable the network to realize n

Terry Gannon

In this paper we find all permutations of the level k weights of the affine algebra A_r^{(1)} which commute with both its S and T modular matrices. We find that all of these are simple current automorphisms and their conjugations. Previously, the A_{r,k}^{(1)} automorphism invariants were known only for r=1,2 \forall k, and k=1 \forall r. This is a major ste

J. Ambjorn, Z. Burda, J. Jurkiewicz, B. Petersson

We measure by Monte Carlo simulations $\g_{string}$ for a model of random surfaces embedded in three dimensional Euclidean space-time. The action of the string is the usual Polyakov action plus an extrinsic curvature term. The system undergoes a phase transition at a finite value $ł_c$ of the extrinsic curvature coupling and at the transition point the numer

A. Niégawa

It has been reported that, within the hard-thermal-loop resummation scheme, the production rate of soft real photons from a hot quark-gluon plasma exhibits unscreened mass singularities. We show that still higher-order resummations screen the mass singularities and obtain the finite soft-photon production rate to leading order at logarithmic accuracy ${\cal

S. Huang, M. Lissia

Within the framework of the operator product expansion (OPE) and the renormalization group equation (RGE), we show that the temperature and chemical potential dependence of the zeroth moment of a spectral function (SF) in an asymptotically free theory is completely determined by the one-loop structure of the theory. This exact result constrains the qualitati

S. Huang, M. Lissia

We generalize the concept of dimensional reduction to operators involving fermion fields in high temperature field theories. It is found that the ultraviolet behavior of the running coupling constant plays a crucial role. The general concept is illustrated explicitly in the Gross-Neveu model.

H. W. Fearing, S. Scherer

We have derived the most general chirally invariant Lagrangian ${\cal L}_6$ for the meson sector at order $p^6$. The result provides an extension of the standard Gasser-Leutwyler Lagrangian ${\cal L}_4$ to one higher order, including as well all the odd intrinsic parity terms in the Lagrangian. The most difficult part of the derivation was developing a syste

J. Lopez, D. Nanopoulos, A. Zichichi

We consider the experimental predictions of two {\em one-parameter} no-scale $SU(5)\times U(1)$ supergravity models with string-inspired moduli and dilaton seeds of supersymmetry breaking. These predictions have been considerably sharpened with the new information on the top-quark mass from the Tevatron, and the actual measurement of the $B(b\to sγ)$ branchi

Xin-Nian Wang, Miklos Gyulassy, Michael Plümer

The non-abelian analog of the Landau-Pomeranchuk-Migdal effect is investigated in perturbative QCD. Extending our previous studies, the suppression of induced soft bremsstrahlung due to multiple scatterings of quarks in the spinor representation is considered. The effective formation time of gluon radiation due to the color interference is shown to depend on

H. Weigel, R. Alkofer, H. Reinhardt

The Bethe--Salpeter equation for pion fluctuations off the chiral soliton in the Nambu--Jona--Lasinio model is constructed. By Goldstone's theorem this equation has rotational and translational zero modes because the classical soliton is a localized stationary field configuration which violates rotational and translational invariance. Furthermore, the pr

Kassa Adel, York-Peng Yao

We present, in the context of dimensional regularization, a prescription to renormalize Feynman diagrams with an arbitrary number of external fermions. This prescription, which is based on the original t'Hooft-Veltman proposal to keep external particles in four dimensions, is particularly useful to define the 'renormalization' (in the context of

B. A. Kniehl, H. -G. Kohrs, G. Kramer

We investigate in detail the effect of a direct pomeron coupling to quarks on the production of jets in $ep$ scattering with almost real photons. Jet production via a direct pomeron coupling is compared with the resolved--pomeron mechanism. We consider both direct and resolved photoproduction. Rapidity and transverse momentum distributions are calculated and

Katsuhiko Suzuki, Hiroshi Toki

We study the masses and the leptonic decay widths of heavy quarkonium in the dual Ginzburg-Landau (DGL) theory of QCD, in which the abelian monopole condensation plays an essential role for color confinement. The effect of color screening due to the light quark pair creation is introduced by the infrared momentum cutoff in the gluon propagator. We find that

Yu. Makeenko

I review some recent work on the problem of multiparticle production in a phi^4-theory with an O(N) symmetry. Threshold amplitudes with fixed number of produced particles are exactly calculated at large-N to all loops and vanish on mass shell for 2->n when n>2 due to a dynamical symmetry. I consider an extension to the cases when the O(N) symmetry is softly

Michael R. Geller, Giovanni Vignale

By using a recently derived upper bound on the allowed equilibrium current in a ring, it is proved that the magnitude of the group velocity of a Bloch electron in a one-dimensional periodic potential is always less than or equal to the group velocity of the same Bloch state in an empty lattice. Our inequality also implies that each energy band in a one-dimen

Kurt Stokbro

In this thesis a new model for calculating the total energy of atomic and solid systems is presented. The model is used to study the properties of the Si(100) surface and dislocation dynamics in the diamond structure. For the Si(100) surface the main result is the finding of an incomplete melted state at $1550^0 K$. The studied dislocation is the $90^0$ part

T. Miyazaki, D. Yoshioka, M. Ogata

Two-dimensional Heisenberg model with anisotropic couplings in the $x$ and $y$ directions ($J_x \neq J_y$) is considered. The model is first solved in the Schwinger-boson mean-field approximation. Then the solution is Gutzwiller projected to satisfy the local constraint that there is only one boson at each site. The energy and spin-spin correlation of the ob

Fernando Pereira, Naftali Tishby, Lillian Lee

We describe and experimentally evaluate a method for automatically clustering words according to their distribution in particular syntactic contexts. Deterministic annealing is used to find lowest distortion sets of clusters. As the annealing parameter increases, existing clusters become unstable and subdivide, yielding a hierarchical ``soft'' cluste

R. A. Battye, E. P. S. Shellard

We discuss radiative backreaction for global strings described by the Kalb-Ramond action with an analogous derivation to that for the point electron in classical electrodynamics. We show how local corrections to the equations of motion allow one to separate the self-field of the string from that of the radiation-field. Modifications to this 'local backre

Donn MacMinn, Joel R. Primack

We present models of the extragalactic background light (EBL) based on several scenarios of galaxy formation and evolution. We have treated galaxy formation with the Press-Schecter approximation for both cold dark matter (CDM) and cold+hot dark matter (CHDM) models. Galaxy evolution has been treated by considering a variety of stellar types, different initia

Timothy R. Klassen

We present a simple parameterization of a running coupling constant, defined via the static potential, that interpolates between 2-loop QCD in the UV and the string prediction in the IR. Besides the usual $\Lam$-parameter and the string tension, the coupling depends on one dimensionless parameter, determining how fast the crossover from UV to IR behavior occ

T. Csorgo B. Lorstad, J. Zimanyi

Quantum statistical correlations and momentum distributions are calculated for a spherically symmetric, three-dimensionally expanding finite fireballs, for non-relativistic expansions applying plane-wave approximation. The new concepts of the geometrical temperature as well as the thermal radius are presented for the simplest case. The symmetry properties of

Neil Marcus, Shimon Yankielowicz

The B-twisted topological sigma model coupled to topological gravity is supposed to be described by an ordinary field theory: a type of holomorphic Chern-Simons theory for the open string, and the Kodaira-Spencer theory for the closed string. We show that the B model can be represented as a PARTICLE theory, obtained by reducing the sigma model to one dimensi

M. Crescimanno, W. Taylor

A matrix model is constructed which describes a chiral version of the large $N$ $U(N)$ gauge theory on a two-dimensional sphere of area $A$. This theory has three separate phases. The large area phase describes the associated chiral string theory. An exact expression for the free energy in the large area phase is used to derive a remarkably simple formula fo

A. Dimakis, F. M"uller-Hoissen, F. Vanderseypen

A `discrete differential manifold' we call a countable set together with an algebraic differential calculus on it. This structure has already been explored in previous work and provides us with a convenient framework for the formulation of dynamical models on networks and physical theories with discrete space and time. We present several examples and int

Heinz König

In this talk I present the contribution of gluinos and scalar quarks to the decay rate of the top quark into a charged Higgs boson and a bottom quark within the minimal supersymmetric standard model, including the mixing of the scalar partners of the left- and right-handed top quark.

Heinz Konig

In this talk I comment on the contributions of all three types of particles (scalars, fermions and bosons) to the three--photon Z decay within the standard model (SM) and its extensions to the 2 Higgs doublet model (2 HDM) and the minimal supersymmetric extension of the standard model (MSSM). I also comment briefly on the charginos contribution to this decay

Alon E. Faraggi

A well known problem in supersymmetric models is the presence of, lepton and baryon number violating, dimension four operators. The traditional R parity solution may not be suitable if one tries to incorporate supersymmetry into a Planck scale theory. I propose a different solution in the context of realistic string models. I show that realistic string model

A. Ali, D. London

Motivated by the recent determination of the top quark mass by the CDF collaboration, $\mt =174 \pm 10 ^{+13}_{-12}$ GeV, we review and update the constraints on the parameters of the quark flavour mixing matrix $V_{CKM}$ in the standard model. In performing our fits, we use inputs from the measurements of the following quantities: (i) $\abseps$, the CP-viol

C. de C. Chamon, D. E. Freed, X. G. Wen

We study non-equilibrium noise in the transmission current through barriers in 1-D Luttinger liquids and in the tunneling current between edges of fractional quantum Hall liquids. The distribution of tunneling events through narrow barriers can be described by a Coulomb gas lying in the time axis along a Keldysh (or non-equilibrium) contour. The charges tend

Devendra Ojha, Olivier Bienayme

We have been doing a sample survey in UBV photometry and proper motions as part of an investigation of galactic structure and evolution. The programme is based on Schmidt plates (from OCA, Tautenburg, Palomar and ESO Schmidt telescopes) digitized with the MAMA machine (CAI, Paris). The high astrometric quality of the MAMA gives access to micronic accuracy (l

Devendra Ojha, Annie C. Robin, Olivier Bienayme

We investigate the kinematics of the intermediate population using the photometric and astrometric sample surveys towards two opposite directions (galactic centre and anticentre) at intermediate latitude. A multivariate discriminant analysis (MDA) is used to distinguish the `Thick Disk' from other populations with the help of the Besan\c con model of pop

Hitoshi Kitada, Lancelot R. Fletcher

The notions of time in the theories of Newton and Einstein are reviewed so that certain of their assumptions are clarified. These assumptions will be seen as the causes of the incompatibility between the two different ways of understanding time, and seen to be philosophical hypotheses, rather than purely scientific ones. The conflict between quantum mechanic

Anatol N. Kirillov

We study the dilogarithm identities from algebraic, analytic, asymptotic, $K$-theoretic, combinatorial and representation-theoretic points of view. We prove that a lot of dilogarithm identities (hypothetically all !) can be obtained by using the five-term relation only. Among those the Coxeter, Lewin, Loxton and Browkin ones are contained. Accessibility of L

C. T. H. Davies, K. Hornbostel, G. P. Lepage, A. Lidsey

We present a new determination of the QCD strong coupling constant based on precise lattice calculations of the $Υ$ spectrum. The largest systematic uncertainty in previous such determinations resulted from the absence of vacuum polarization from light quarks. We substantially reduce this error by including two flavors of dynamical light quarks and extrapola

S. Kumano

SU(2)-flavor-symmetry breaking in antiquark distributions of the nucleon was suggested by the New Muon Collaboration (NMC) in deep inelastic muon scattering. As an independent test, Drell-Yan data for the tungsten target have been used for examining the asymmetry. We investigate whether there exists significant modification of the $\bar u -\bar d$ distributi

S. Narison

We determine the $SU(3)$-breaking effects in the $\bar{B}/D \rar Kl\bar ν$ decays from the ratio of the $\bar{B}/D\rar Kl\bar ν$ over the $\bar{B}/D \rar πl\bar ν$ semileptonic form factors using a {\it semi-analytic} expression based on QCD spectral sum rules. We obtain $f_+^{\bar{B}\rar K}(0)/f_+^{\bar{B} \rar π}(0)$ = $1.007\pm 0.020$ and $f_+^{D\rar K}(0

Tiehui, Liu

The search for $D^0\bar{D}^0$ mixing carries a large discovery potential for new physics since the $D^0\bar{D}^0$ mixing rate is expected to be very small in the Standard Model. The past decade has seen significant experimental progress in sensitivity, from 20\% down to 0.37\%. This paper discusses the techniques, current experimental status, and future pros

D. Amidei, A. Baden, G. Foster, G. Jackson

The Fermilab Tevatron will be the world's highest energy hadron collider until the LHC is commissioned, it has the world's highest energy fixed target beams, and Fermilab will be the leading high energy physics laboratory in the US for the foreseeable future. Following the demise of the SSC, a number of possible upgrades to the Tevatron complex, beyo

Craig D. Roberts

It is shown that the solution of the quark Dyson-Schwinger equation in QCD obtained with a gluon propagator of the form $D(q) \sim q^2/[q^4+b^4]$ and a quark-gluon vertex that is free of kinematic singularities does not describe a confined particle and that there is always a value of $b^2 = b^2_c$ such that chiral symmetry is not dynamically broken for $b^2>

W. T. Giele, S. Keller, E. Laenen

We summarize the motivations for and the status of the calculation of the $W +$ heavy quark production process in $p \bar p$ colliders to Next-to-Leading Order in QCD. This process can be used to constrain the strange quark distribution function at high $Q^2$ at the Tevatron, and also to study the bottom content of $W+1$~jet events. In addition, when crossed

C. W. J. Beenakker

The distribution function of the local density of states is computed exactly for the Wigner-Dyson ensemble of random Hamiltonians. In the absence of time-reversal symmetry, precise agreement is obtained with the "supersymmetry" theory by Efetov and Prigodin of the NMR lineshape in disordered metal particles. Upon breaking time-reversal symmetry, the variance

Th. M. Nieuwenhuizen

A mean field spherical model with random couplings between pairs, quartets, and possibly higher multiplets of spins is considered. It has the same critical behavior as the Sherrington-Kirkpatrick model. It thus exhibits replica symmetry breaking. The order parameter function is solved exactly in the whole low temperature phase. The zero field cooled suscepti

Th. M. Nieuwenhuizen

The spherical model for spins describes ferromagnetic phase transitions well, but it fails at low temperatures. A quantum version of the spherical model is proposed. It does not induce qualitative changes near the phase transition. However, it produces a physical low temperature behavior. The entropy is non-negative. Model parameters can be adapted to the de

T. Kobayashi, D. Suematsu, K. Yamada, Y. Yamagishi

We study soft scalar masses comparing with gaugino masses in 4-dimensional string models. In general non-universal soft masses are derived in orbifold models. We give conditions on modular weights to lead to the large non-universality in the soft scalar masses. This non-universality is applied to the unification of the gauge coupling constants in the minimal

O. A. Soloviev

We consider two level $k$ WZNW models coupled to each other through a generalized Thirring-like current-current interaction. It is shown that in the large $k$ limit, this interacting system can be presented as a two-parameter perturbation around a nonunitary WZNW model. The perturbation operators are the sigma model kinetic terms with metric related to the T

W. Zippold

Using a representation of the q-deformed Lorentz algebra as differential operators on quantum Minkowski space, we define an algebra of observables for a q-deformed relativistic quantum mechanics with spin zero. We construct a Hilbert space representation of this algebra in which the square of the mass $ p^2 $ is diagonal.

Yakov Kanter

Greene, Morrison and Plesser \cite{GMP} have recently suggested a general method for constructing a mirror map between a $d$-dimensional Calabi-Yau hypersurface and its mirror partner for $d > 3$. We apply their method to smooth hypersurfaces in weighted projective spaces and compute the Chern numbers of holomorphic curves on these hypersurfaces. As anticipa

Hilmar Forkel, Marina Nielsen, Xuemin Jin, Thomas D. Cohen

A model combining vector meson dominance, $ω- ϕ$ mixing and a kaon cloud contribution is used to estimate the strangeness vector form factors of the nucleon in the momentum range of the planned measurements at MIT-Bates and CEBAF. We compare our results with some other theoretical estimates and discuss the nucleon strangeness radius in models based on dynami

David H. Lyth, Ewan D. Stewart

Recent work is reported on inflation model building in the context of supergravity and superstrings, with special emphasis on False Vacuum (`Hybrid') Chaotic Inflation. Globally supersymmetric models do not survive in generic supergravity theories, but fairly simple conditions can be formulated which do ensure successful supergravity inflation. The condi

V. Bernard

I present some recent results on neutral pion photo- and electroproduction in the threshold region and discuss the low energy theorem for $E_{0+}$ and some novel ones for the $P$-waves. I also study the two-pion production process $γN \to ππN$ from which complementary information can be gained.

M. Kawasaki, T. Moroi

Gravitino produced in the inflationary universe are studied. When the gravitino decays into a neutrino and a sneutrino, the emitted high energy neutrinos scatter off the background neutrinos and produce charged leptons (mainly electrons and positrons), which cause the electro-magnetic cascades and produce many soft photons. We obtain the spectra of the high

S. Catterall, J. Kogut, R. Renken

We present numerical results supporting the existence of an exponential bound in the dynamical triangulation model of three-dimensional quantum gravity.Both the critical coupling and various other quantities show a slow power law approach to the infinite volume limit.

D. H. Coule

We consider the claim of Hawking and Page that the canonical measure applied to a FRW universe with a massive scalar field can solve the flatness problem regardless of inflation. By considering a general potential we are able to understand how the ambiguity for $Ω$ found by Page in the $R^2$ theory is present when the potential is bounded from above. We sugg

E. Bruning, D. Coule, C. Xu

We consider an alternative higher order gravity theory which is non-analytic in the Ricci curvature. It has power-law inflationary behaviour. This is further evidence that inflation is a general property of higher derivative gravity theories.

D. H. Coule

We analyse a simple model with just a $Λ$ term present. Differing results are obtained depending on the boundary conditions applied. HH boundary conditions give the factor exp(1/Lambda) but in agreement with Rubakov et al. is badly behaved for negative lambda. Tunneling boundary conditions suggests a large initial lambda. If only a Lorentzian region is consi

Rob Kusner, Rafe Mazzeo, Daniel Pollack

We examine the space of surfaces in $\RR^{3}$ which are complete, properly embedded and have nonzero constant mean curvature. These surfaces are noncompact provided we exclude the case of the round sphere. We prove that the space $\Mk$ of all such surfaces with $k$ ends (where surfaces are identified if they differ by an isometry of $\RR^{3}$) is locally a r

Hua Wu, D. W. L. Sprung

Ballistic transport of electrons through a quantum wire with a constriction is studied in terms of Bohm's interpretation of quantum mechanics, in which the concept of a particle orbit is permitted. The classical bouncing ball trajectories, which justify the name ``ballistic transport'', are established in the large wave number limit. The formatio

Ian Affleck, Martin P. Gelfand, Rajiv R. P. Singh

The $S=1/2$, nearest-neighbor, quantum Heisenberg antiferromagnet on the square lattice with spatially anisotropic couplings is reconsidered, with particular attention to the following question: at T=0, does Néel orderdevelop at infinitesimal interchain coupling, or is there a nonzero critical coupling? A heuristic renormalization group argument is presented

G. S. Uhrig

Spinless fermions with repulsion are treated non-perturbatively by classifying the diagrams of the generating functional $Φ$ in powers of the inverse lattice dimension $1/d$. The equations derived from the first two orders are evaluated on the one- and on the two-particle level. The order parameter of the AB-charge density wave (AB-CDW) occurring at larger i