February 1995 arXiv papers — page 4

Harald H. Soleng

CARTAN is an easy-to-use symbolic, tensor component package based on the popular Mathematica program. CARTAN makes use of the powerful formalism of rigid frames, and can return results both in this frame and in the coordinate basis. CARTAN has predefined functions for computation of tensors such as Riemann, Ricci, Einstein, Weyl, as well as other tensors and

Valentin V. Khoze

Anomalous fermion number violation is studied in the background of a pure SU(2) gauge field in Minkowski space using the method of N. Christ. It is demonstrated that the chiral fermion number is violated by at most an integer amount. Then the method is applied for a spherically symmetric Minkowski space classical gauge field in the background. These classica

R. D. Ball, S. Forte, G. Ridolfi

We discuss perturbative evolution of the polarized structure function g_1 in the (x,Q^2) plane, with special regard to the small-x region. We determine g_1 in terms of polarized quark and gluon distributions using coefficient functions to order alpha_s. At small x g_1 then displays substantial scale dependence, which necessarily implies a corresponding scale

A. Gonzalez-Arroyo, P. Martinez

We study thermalised configurations of SU(2) gauge fields by cooling. An analysis of the effect of cooling is presented and global and statistical information is extracted.

Bela Szilagyi, Romeo Susan -- Resiga, Victor Sofonea

Four different kinds of laminar flows between two parallel plates are investigated using the Lattice Boltzmann Method (LBM). The LBM accuracy is estimated in two cases using numerical fits of the parabolic velocity profiles and the kinetic energy decay curves, respectively. The error relative to the analytical kinematic viscosity values was found to be less

A. S. Cattaneo, P. Cotta-Ramusino, A. Gamba, M. Martellini

We study the first-order formalism of pure four-dimensional ${\rm SU}(2)$ Yang--Mills theory with theta-term. We describe the Green functions associated to electric and magnetic flux operators à la 't~Hooft by means of gauge-invariant non-local operators. These Green functions are related to Witten's invariants of four-manifolds.

K. Fabricius, U. Löw, K. -H. Mütter

The finite size effects of the dynamical structure factors in the XXZ-model are studied in the euclidean time $(τ)$-representation. Away from the critical momentum $p=π$ finite size effects turn out to be small except for the large $τ$ limit. The large finite size effects at the critical momentum $p=π$ signal the emergence of infrared singularities in the sp

S. J. Dong, J. -F. Lagae, K. F. Liu

We report on a lattice QCD calculation of the flavor-singlet axial coupling constant $g_A$ of the proton from the axial-vector current. The simulation is carried out at $β= 6$ on a quenched $16^3 \times 24$ lattice. An extrapolation to the chiral limit shows that the connected insertion (valence and cloud parts) is $0.62 \pm 0.09$, which is close to $g_A^8$.

Meng-yuan Wang

We develop a systematic treatment for the quasi-zero modes, which play an important role in nonabelian gauge theories. It can be used to derive the analytic forms for the constrained instantons in the \ymh theory. This will automatically sum up contributions to all orders in $ρ$, the instanton size. We also give the analytic expressions for the instanton-ant

K. Wodkiewicz

Einstein Podolsky Rosen quantum correlations are discussed from the perspective of a ghost field introduced by Einstein. The concepts of ghost field, hidden variables, local reality and the Bell inequality are reviewed. In the framework of the correlated singlet state, it is shown that quantum mechanics can be cast in a way that has the form of either nonpos

Karl-Peter Marzlin, Juergen Audretsch

The time evolution of a two-level atom which is simultaneously exposed to the field of a running laser wave and a homogeneous gravitational field is studied. The result of the coupled dynamics of internal transitions and center-of-mass motion is worked out exactly. Neglecting spontaneous emission and performing the rotating wave approximation we derive the c

Tetsuya Kawagishi, Tsuyoshi Mizuguchi, Masaki Sano

In an experiment of oscillatory media, domains and walls are formed under the parametric resonance with a frequency double the natural one. In this bi-stable system, %phase jumps $π$ by crossing walls. a nonequilibrium transition from Ising wall to Bloch wall consistent with prediction is confirmed experimentally. The Bloch wall moves in the direction determ

Thomas A. Kaeding

The Clebsch-Gordan coefficients of $SU(3)$ are useful in calculations involving baryons and mesons, as well as in calculations involving arbitrary numbers of quarks. For the latter case, one needs the coupling constants between states of nonintegral hypercharges. The existing published tables are insufficient for many such applications, and therefore we have

Alphonse P. Magnus

Difference calculus compatible with polynomials (i.e., such that the divided difference operator of first order applied to any polynomial must yield a polynomial of lower degree) can only be made on special lattices well known in contemporary $q-$calculus. Orthogonal polynomials satisfying difference relations on such lattices are presented. In particular, l

Pablo Arés Gastesi

In this paper we parametrize the Teichmüller spaces of constructible Koebe groups, that is Kleinian group that arise as covering of $2-$orbifolds determined by certain normal subgroups of their fundamental groups. We also study the covering spaces of the Teichmüller spaces of those Koebe groups. Finally we prove an isomorphisms theorem similar to the Bers-Gr

M. Gasperini, M. Giovannini

We show that the effective coarse graining of a two-mode squeezed density matrix, implicit in the Wehrl approaches to a semiclassical phase-space distribution, leads to results in agreement with previous different definitions of entropy for the process of pair production from the vacuum. We also present, in this context, a possible interpretation of the entr

I. L. Shapiro, Hiroyuki Takata

We study the one loop renormalization in the most general metric-dilaton theory with the second derivative terms only. The general theory can be divided into two classes, models of one are equivalent to conformally coupled with gravity scalar field and also to general relativity with cosmological term. The models of second class have one extra degree of free

Emil Mottola

The geometric construction of the functional integral over coset spaces ${\cal M}/{\cal G}$ is reviewed. The inner product on the cotangent space of infinitesimal deformations of $\cal M$ defines an invariant distance and volume form, or functional integration measure on the full configuration space. Then, by a simple change of coordinates parameterizing the

S. Kelley

I derive conservative upper bounds on the supersymmetry breaking parameter $m_{1/2}$ as a function of the strong coupling in the Standard Supersymmetric Model (SSM) using gauge coupling unification. I find that over more than $99\%$ of the parameter space, $α_3>0.120$ implies that $m_{1/2}$ is below $10\TeV$ and $α_3>0.129$ implies that $m_{1/2}$ is below $1

Dimitris Kominis

We discuss possible signatures of the $CP$-odd scalar of two-doublet models at the LHC. We find that the inclusive two-photon decay mode and the decay sequence $A^0 \rightarrow Zh, h \rightarrow γγ$, where $h$ is a $CP$-even neutral scalar, can give viable signals in fairly large and complementary regions of parameter space.

N. Kidonakis, J. Smith

The inclusive transverse momentum and rapidity distributions for top quark production at the Fermilab Tevatron are presented both in order $α_s^3$ in QCD and using the resummation of the leading soft gluon corrections in all orders of QCD perturbation theory. The resummed results are uniformly larger than the $O(α_s^3)$ results for both distributions.

Zhi-zhong Xing

To lowest-order weak interactions in the standard model, we point out that a complete graph description of two-body mesonic $B$ (or $D$) decays needs ten topologically different quark diagrams. The two-body baryonic $B$ decays can be illustrated in terms of five diagrams. We remark a variety of features of the graph language. Some pure channels of mesonic $B

E. Bagan, Patricia Ball, B. Fiol, P. Gosdzinsky

We calculate the complete ${\cal O}(α_s)$ corrections to the quark decay $b\to ccs$ taking full account of the quark masses, but neglecting penguin contributions. For a c to the b quark mass ratio $m_c/m_b= 0.3$ and a strange quark mass of $0.2\,$GeV, we find that the next-to-leading order (NLO) corrections increase $Γ(b\to ccs)$ by $(32\pm 15)\%$ with respe

Dongsheng Du, Zhi-zhong Xing

The space-like penguin contributions were ignored on little ground in many previous studies of nonleptonic B decays and CP violation. Taking the penguin-dominated channels $B^{-} _{u}\rightarrow \bar{K}^{0}π$ and $B^{-}_{u}\rightarrow K^{0} K^{-}$ for example, we illustrate the non-negligible effects of the space-like penguin diagrams on CP asymmetries. Some

A. D. Martin, R. G. Roberts, W. J. Stirling

The latest measurements of $F_2$ at HERA allow for a {\it combination} of gluon and sea quark distributions at small $x$ that is significantly different from those of existing parton sets. We perform a new global fit to deep-inelastic and related data. We find a gluon distribution which is larger for $x \lapproxeq 0.01$, and smaller for $x \sim 0.1$, and a f

Johan Bijnens

We discuss the low-energy analysis of models involving quarks and four-fermion couplings. The relation with QCD and with other models of mesons and meson plus quarks at low energies is discussed. A short description of how the heat-kernel expansion can be used to get regularization independent information, is given. The anomaly within this class of models an

Meng-yuan Wang

We show why and how the $I\bar I$ valley trajectory commonly used in the literature so far is in fact unsatisfactory. A better $I\bar I$ valley is suggested. We also give analytic expressions for the multiple instanton-antiinstanton configurations in the pure Yang-Mills theory. These formulas make it possible to go beyond the dilute gas approximation and cal

Kostas D. Kokkotas, Gerhard Schaefer

Tidal and tidal-resonant effects in coalescing compact binary systems are investigated by direct numerical integration of the equations of motion. For the stars polytropic models are used. The tidal effects are found to be dominated by the (non-resonant) $f$-modes. The effect of the $g$-mode-tidal resonances is obtained. The tidal interaction is shown to be

Gérard Clément

We construct regular multi-wormhole solutions to a gravitating $σ$ model in three space-time dimensions, and extend these solutions to cylindrical traversable wormholes in four and five dimensions. We then discuss the possibility of identifying wormhole mouths in pairs to give rise to Wheeler wormholes. Such an identification is consistent with the original

Manuel Fuentes, Ana Lopez, Eduardo Fradkin, Enrique Moreno

We derive the bosonization rules for free fermions on a half-line with physically sensible boundary conditions for Luttinger fermions. We use path-integral methods to calculate the bosonized fermionic currents on the half-line and derive their commutation relations for a system with a boundary. We compute the fermion determinant of the fermionic fluctuations

Leticia F. Cugliandolo, David S. Dean

We present a detailed analysis for the Langevin dynamics of a spherical spin-glass model (the spherical Sherrington-Kirkpatrick model). All the spins in the system are coupled by pairs via a random interaction matrix taken from the Gaussian ensemble. One finds that for a general initial configuration the system never reaches an equilibrium state and the theo

Frederic Mila

Numerical calculations of the kinetic energy of various extensions of the one-dimensional Hubbard model including dimerization and repulsion between nearest neighbours are reported. Using the sum rule that relates the kinetic energy to the integral of the optical conductivity, one can determine which parameters are consistent with the reduction of the infrar

Frederic Mila, Karlo Penc

We show that the zero temperature susceptibility of the one-dimensional, dimerized Hubbard model at quarter-filling can be accurately determined on the basis of exact diagonalization of small clusters. The best procedure is to perform a finite-size scaling of the spin velocity $u_σ$, and to calculate the susceptibility from the Luttinger liquid relation $χ=2

M. E. Portnoi, E. I. Rashba

A theory of anyon excitons consisting of a valence hole and three quasielectrons with electric charges $(-e/3)$ is presented. A full symmetry classification of the $k=0$ states is given, where $k$ is the exciton momentum. The energy levels of these states are expressed by quadratures of confluent hypergeometric functions. It is shown that the angular momentu

Chris Brew

In this paper we provide a probabilistic interpretation for typed feature structures very similar to those used by Pollard and Sag. We begin with a version of the interpretation which lacks a treatment of re-entrant feature structures, then provide an extended interpretation which allows them. We sketch algorithms allowing the numerical parameters of our pro

Bill Keller, David Weir

It has been shown that Linear Indexed Grammars can be processed in polynomial time by exploiting constraints which make possible the extensive use of structure-sharing. This paper describes a formalism that is more powerful than Linear Indexed Grammar, but which can also be processed in polynomial time using similar techniques. The formalism, which we refer

Thomas V. Russo, Richard L. Martin, P. Jeffrey Hay

Density functional theory(DFT) and Hartree-Fock(HF) calculations are reported for the family of transition metal fluorides $\mbox{ScF}_3$, $\mbox{TiF}_4$, $\mbox{VF}_5$, and $\mbox{CrF}_6$. Both HF and the local-density-aproximation (LDA) yield excellent agreement with experimental bond lengths, while the B-LYP gradient-corrected density functional gives bon

Carsten Peterson, Ola Sommelius, Bo Söderberg

A variational method for computing conformational properties of molecules with Lennard-Jones potentials for the monomer-monomer interactions is presented. The approach is tailored to deal with angular degrees of freedom, {\it rotors}, and consists in the iterative solution of a set of deterministic equations with annealing in temperature. The singular short-

Anders Irback, Holm Schwarze

We study the thermodynamic behavior of the random chain model proposed by Iori, Marinari and Parisi, and how this depends on the actual sequence of interactions along the chain. The properties of randomly chosen sequences are compared to those of designed ones, obtained through a simulated annealing procedure in sequence space. We show that the transition to

Slavek Rucinski, David Dunlap Observatory

12 W~UMa-type systems were observed at 3.6 cm with a goal to compare their radio luminosities with those of non-contact, rapidly rotating, late-type stars. Only 3 systems, all of spectral type K, have been detected. The detections and (low) upper limits for remaining systems confirm the strong under-luminosity of W~UMa-type systems. VW~Cep, which was been de

George M. Fuller, Joel R. Primack, Yong-Zhong Qian

The recent results from the Los Alamos neutrino oscillation experiment, together with assumptions of neutrino oscillation solutions for the solar and atmospheric neutrino deficit problems, may place powerful constraints on any putative scheme for neutrino masses and mixings. Assuming the validity of these experiments and assumptions, we argue that a nearly u

Yong-Zhong Qian, George M. Fuller

Matter-enhanced antineutrino flavor transformation between $\barν_e$ and $\barν_{μ(τ)}$ can occur in supernovae if the vacuum masses for these species satisfy $m_{\barν_e}>m_{\barν_{μ(τ)}}$. For $δm^2> 1$ eV$^2$, such flavor transformation can affect the electron fraction $Y_e$ in the neutrino-heated supernova ejecta. We point out that such flavor transforma

R. Pandharipande

A projective moduli space of pairs (C,E) where E is a slope- semistable torsion free sheaf of uniform rank on a Deligne- Mumford stable curve C is constructed via G.I.T. There is a natural SL x SL action on the relative Quot scheme over the universal curve of the Hilbert scheme of pluricanonical, genus g curves. The G.I.T. quotient of this product action yie

V. Balaji, A. D. King, P. E. Newstead

Let $\MC$ be the moduli space of stable holomorphic vector bundles of rank 2 and fixed determinant of odd degree, over a smooth projective curve $C$. This paper identifies the algebraic cohomology ring $\HA^*(\MC)$, i.e. the subring of the rational cohomology ring $H^*(\MC;\QQ)$ spanned by the fundamental classes of algebraic cycles, in terms of the algebrai

H. Lu, C. N. Pope, K. S. Stelle, K. W. Xu

We investigate new realisations of the $W_3$ algebra with arbitrary central charge, making use of the fact that this algebra can be linearised by the inclusion of a spin-1 current. We use the new realisations with $c=102$ and $c=100$ to build non-critical and critical $W_3$ BRST operators. Both of these can be converted by local canonical transformations int

Pyungwon Ko, Kang Young Lee, Jae Kwan Kim

We consider a process $K_{L e5} ( K_{L} \rightarrow π^{0} π^{0} π^{\pm} e^{\mp} ν)$ as a standard model background to the experiment $K_{L} \rightarrow π^{0} μ^{\pm} e^{\mp}$, which seeks for possible violation of lepton family number. Using the lowest order chiral lagrangian, we find that the branching ratio for $K_{L} \rightarrow π^{0} π^{0} π^{\pm} e^{\mp

Koji Harada, Atsusi Okazaki, Masa-aki Taniguchi

The spectrum of the massive Schwinger model in the strong coupling region is obtained by using the light-front Tamm-Dancoff (LFTD) approximation up to including six-body states. We numerically confirm that the two-meson bound state has a negligibly small six-body component. Emphasis is on the usefulness of the information about states (wave functions). It is

Andreas Wirzba, Vesteinn Thorsson

We argue that the effective pion mass in nuclear matter obtained from chiral effective lagrangians is unique and does not depend on off-mass-shell extensions of the pion fields as e.g. the PCAC choice. The effective pion mass in isospin symmetric nuclear matter is predicted to increase slightly with increasing nuclear density, whereas the effective time-like

Kei-Ichi Kondo

Starting from a reformulation of the Thirring model as a gauge theory, we consider the bosonization of the $D$-dimensional multiflavor massive Thirring model $(D \ge 2)$ with four-fermion interaction of the current-current type. Our method leads to a novel interpolating Lagrangian written in terms of two gauge fields. Especially we pay attention to the case

B. Shklyar

An observability problem for linear autonomous distributed systems in the class of linear operations is considered. A criterion of observability with respect to terminal state has been proved. A connection with observability with respect to initial state is discussed.

Juan P. Aparicio, Fabian H. Gaioli, Edgardo T. Garcia Alvarez

The Feynman parametrization of the Dirac equation is considered in order to obtain an indefinite mass formulation of relativistic quantum mechanics. It is shown that the parameter that labels the evolution is related to the proper time. The Stueckelberg interpretation of antiparticles naturally arises from the formalism.

H. -D. Doebner, G. A. Goldin, P. Nattermann

We examine a recently-proposed family of nonlinear Schrödinger equations [J. Phys. A: Math. Gen. 27:1771(1994)] with respect to a group of transformations that linearize a subfamily of them. We investigate the structure of the whole family with respect to the linearizing transformations, and propose a new, invariant parameterization.

Anna Beliakova, Bergfinnur Durhuus

We prove in the context of quantum groups at even roots of unity that a Turaev-Viro type invariant of a 3-dimensional cobordism M equals the tensor product of the Reshetikhin-Turaev invariants of M and M*, where M* denotes M with orientation reversed.

Daniel Gordon, Greg Kuperberg, Oren Patashnik

A $(v,k,t)$ {\em covering design}, or {\em covering}, is a family of $k$-subsets, called blocks, chosen from a $v$-set, such that each $t$-subset is contained in at least one of the blocks. The number of blocks is the covering's {\em size}, and the minimum size of such a covering is denoted by $C(v,k,t)$. This paper gives three new methods for constructi

Katrin Becker, Melanie Becker, Andrew Strominger

Witten has argued that in $2+1$ dimensions local supersymmetry can ensure the vanishing of the cosmological constant without requiring the equality of bose and fermi masses. We find that this mechanism is implemented in a novel fashion in the (2+1)-dimensional supersymmetric abelian Higgs model coupled to supergravity. The vortex solitons are annihilated by

Michael Gutperle

String amplitudes with an arbitrary number of world-sheet boundaries on which the coordinates satisfy Dirichlet boundary conditions are analyzed in a path integral framework. Special attention is payed to the novel divergences associated with such conditions. Certain helicity amplitudes involving massless closed-string states are free of such divergences to

G. Amelino-Camelia

I discuss two techniques that can be used in the investigation of the properties of ``colliding" and ``non-colliding" anyons.

Franco Ferrari

The massive scalar field theory and the chiral Schwinger model are quantized on a Poincaré disk of radius $ρ$. The amplitudes are derived in terms of hypergeometric functions. The behavior at long distances and near the boundary of some of the relevant correlation functions is studied. The exact computation of the chiral determinant appearing in the Schwinge

Andreas Peter, Joern M. Haeuser, Markus H. Thoma, Wolfgang Cassing

We apply a truncated set of dynamical equations of motion for connected equal-time Green functions up to the 4-point level to the investigation of spontaneous ground state symmetry breaking in $Φ^4_{2+1}$ quantum field theory. Within our momentum space discretization we obtain a second order phase transition as soon as the connected 3-point function is inclu

S. ICHINOSE, N. TSUDA, T. YUKAWA

Two dimensional quantum R$^2$-gravity and its phase structure are examined in the semiclassical approach and compared with the results of the numerical simulation. Three phases are succinctly characterized by the effective action. A classical solution of R$^2$-Liouville equation is obtained by use of the solution of the ordinary Liouville equation. The parti

Mirjam Cvetic, Donam Youm

Static, four-dimensional (4-d) black holes (BH's) in ($4+n$)-d Kaluza-Klein (KK) theory with Abelian isometry and diagonal internal metric have at most one electric ($Q$) and one magnetic ($P$) charges, which can either come from the same $U(1)$-gauge field (corresponding to BH's in effective 5-d KK theory) or from different ones (corresponding to BH

Sukanta Bose, Leonard Parker, Yoav Peleg

We study a modified two-dimensional dilaton gravity theory which is exactly solvable in the semiclassical approximation including back-reaction. The vacuum solutions of this modified theory are asymptotically flat static space-times. Infalling matter forms a black hole if its energy is above a certain threshold. The black hole singularity is initially hidden

Eric Sather, Witold Skiba

We consider the Strongly-Coupled Standard Model (Abbott-Farhi model) including an isotriplet of W' vector bosons. First we calculate the corrections to the low-energy theory, which can be effectively summarized in terms of the parameters S, T and U. Then we use high- precision electroweak measurements to constrain the mass and couplings of the W'. Th

Apostolos Pilaftsis

In view of the recent and future electroweak precision data accumulated at LEP and SLC, we systematically analyze possible new physics effects that may occur in the leptonic sector within the context of $SU(2)_R \times SU(2)_L \times U(1)_{B-L}$ theories. It is shown that nonobservation of flavour-violating $Z$-boson decays, lepton universality in the decays

Gustavo Burdman, Eugene Golowich, JoAnne L. Hewett, Sandip Pakvasa

We address Standard Model predictions for flavor-changing radiative transitions of the pseudoscalar charm mesons. Short-distance contributions in $D$ radiative transitions are contrasted with those in B decays. A full analysis is presented of the $c\to u+γ$ electromagnetic penguin amplitude with QCD radiative corrections included. Given the importance of lon

U. Zückert, R. Alkofer, H. Weigel, H. Reinhardt

In the Nambu--Jona-Lasinio model baryons are either considered as quark-diquark-composites or the soliton configurations of the model are interpreted as baryons. As a first step towards constructing a hybrid model, which possesses a dynamical interplay between both pictures, the Bethe-Salpeter equation for diquarks in the background of a soliton configuratio

Glennys Farrar

The physics of electroweak baryogenesis is described with the aim of making the essentials clear to non-experts. Several models for the source of the necessary CP violation are discussed: CKM phases as in the minimal standard model, general two higgs doublet models, the supersymmetric standard model, $Z$ condensates, and the singlet majoron model. In a more

Hua-Bin Tang, R. J. Furnstahl

An expression for the photon condensate in quantum electrodynamics is presented and generalized to deduce a simple relation between the gluon condensate and the running coupling constant of quantum chromodynamics (QCD). Ambiguities in defining the condensates are discussed. The values of the gluon condensate from some Ansätze for the running coupling in the

R. Casalbuoni, P. Chiappetta, A. Deandrea, S. De Curtis

We present some results on the usefulness of upgraded Tevatron, LHC proton proton collider and linear e+e- colliders in the TeV range to test the idea of a strongly interacting sector as responsible for the electroweak symmetry breaking. The calculations are performed within an effective lagrangian description, called the BESS model, which provides for a rat

F. Flechsig, A. K. Rebhan, H. Schulz

All the next-to-leading order contributions to the quasi-particle dispersion laws of a quark-gluon plasma which due to infrared singularities are sensitive to the magnetic-mass scale are calculated using Braaten-Pisarski resummation. These relative-order-$g\ln(g)$ corrections are shown here to generally contribute to the dynamical screening of gluonic fields

E. Stein, P. Gornicki, L. Mankiewicz, A. Schaefer

We calculate the twist-4 corrections to the integral of $g_1(x,Q^2)$ in the framework of QCD sum rules using an interpolating nucleon field which contains explicitly a gluonic degree of freedom. This information can be used together with previous calculations of the twist-3 contribution to the second moment of $g_2(x)$ to estimate the higher-twist correction

H. Satz

Direct probes for the QGP must be hard enough to resolve sub-hadronic scales ($\ll \la^{-1}$) and distinguish confined and deconfined media. This can be achieved by fast colour charges (jets) and heavy quark resonances (quarkonia). After a general survey, we study quarkonia as confinement probe and show in particular that confined matter is transparent, deco

W. Buchmuller, Z. Fodor, A. Hebecker

We discuss several general aspects of the free energy of the standard model at high temperatures. In particular the Clausius-Clapeyron equation is shown to yield a relation between the latent heat and the jump in the order parameter. The free energy is calculated as function of temperature in resummed perturbation theory to two-loop order. A new resummation

R. Engel, J. Ranft, S. Roesler

Hard single diffractive processes are studied within the framework of the triple--Pomeron approximation. Using a Pomeron structure function motivated by Regge--theory we obtain parton distribution functions which do not obey momentum sum rule. Based on Regge-- factorization cross sections for hard diffraction are calculated. Furthermore, the model is applied

Costas Kounnas, Ilarion Pavel, Giovanni Ridolfi, Fabio Zwirner

Motivated by four-dimensional superstring models, we consider the possibility of treating the Yukawa couplings of the Minimal Supersymmetric Standard Model (MSSM) as dynamical variables of the effective theory at the electroweak scale. Assuming bottom-tau unification, we concentrate on the top and bottom Yukawa couplings, and find that minimizing the effecti

David Garcia, Joan Sola

We study the correlation of quantum effects on the ratios R_b and R_c within the framework of the MSSM. While in the SM the quantity R_b is in discrepancy with experiment at the 2 σlevel from below, and R_c differs from the experimental result at the 1.5 σlevel from above, the theoretical prediction for both observables could simultaneously improve in the MS

G. I. Lykasov, M. N. Sergeenko

A new approach to the analysis of soft and semihard hadron processes is suggested. In the frame of the Quark-Gluon String Model the interaction of valence quarks and diquarks and sea quarks (antiquarks) of colliding hadrons is taken into account. This one is calculated as the exchange by one nonpertubative gluon, i.e., the cut-off parameter in the gluonic pr

M. Hirsch, H. V. Klapdor-Kleingrothaus, S. G. Kovalenko

The neutrinoless double beta ($\znbb$) decay is analyzed within the Minimal Supersymmetric Standard Model with explicit R-parity violation (\rp MSSM). We have found new supersymmetric contributions to this process and give the complete set of relevant Feynman diagrams. Operators describing $0^+ \longrightarrow 0^+$ nuclear transitions induced by the supersym

Antal Jakovac

Dimensional reduction of high temperature field theories improves IR features of their perturbative treatment. A crucial question is, what three-dimensional theory is representing the full system the most faithful way. Careful investigation of the induced 3-dimensional counterterm structure of the finite temperature 4D O(N) symmetric scalar theory at 2-loop

C. Glenn Boyd, Benjamin Grinstein

We compute the O(1/M,m_s) heavy quark and SU(3) corrections to B_s -> D_s e nu form factors. In the limit of vanishing light quark mass, B_s -> D_s e nu form factors are given in terms of the the B -> D e nu form factors, the leading order chiral parameter g, and two O(1/M) chiral parameters $g_1$ and $g_2$. All the chiral parameters can be extracted, in pri

C. R. Allton, M. Crisafulli, V. Lubicz, G. Martinelli

The decay constant for the B-meson in the static limit is calculated using the Wilson and clover actions at various lattice spacings. We show that both the contamination of our results by excited states and the effects finite lattice spacing are at most the order of the statistical uncertainties. A comparison is made of our results and those obtained in othe

M. Crisafulli, V. Lubicz, G. Martinelli, A. Vladikas

We study the behaviour of the vector and axial current renormalisation constants $Z_V$ and $Z_A$ as a function of the quark mass, $m_q$. We show that sizeable $O(am_q)$ and $O(g_0^2 a m_q)$ systematic effects are present in the Wilson and Clover cases respectively. We find that the prescription of Kronfeld, Lepage and Mackenzie for correcting these artefacts

O. E. Buryak

In this paper we derive exact quantum Langevin equations for stochastic dynamics of large-scale inflation in de~Sitter space. These quantum Langevin equations are the equivalent of the Wigner equation and are described by a system of stochastic differential equations. We present a formula for the calculation of the expectation value of a quantum operator who

Sergey A. Merkulov

It is shown that any irreducible analytic 1-flat $G$-structure as well as any analytic torsion-free affine connection with irreducibly acting holonomy group can, in principle, be contstructed by twistor methods.

David R. Nelson

An introduction to the defects which dominate the physics of superfluid He$^4$ films, of superconducting slabs and of crystalline and hexatic membranes is given. We first review point vortices in two-dimensional neutral superfluids and discuss the unusual screening which arises when the bosons are charged, as in superconducting films. Dislocation and disclin

Nathan Argaman

The Kubo formula for the conductance of classically chaotic systems is analyzed semiclassically, yielding simple expressions for the mean and the variance of the quantum interference terms. In contrast to earlier work, here times longer than $O( \log \hbar^{-1} )$ give the dominant contributions, i.e. the limit $\hbar \rightarrow 0$ is not implied. For examp

F. Corberi, A. Coniglio, M. Zannetti

A global analysis of the scaling behaviour of a system with a scalar order parameter quenched to zero temperature is obtained by numerical simulation of the Ginzburg-Landau equation with conserved and non conserved order parameter. A rich structure emerges, characterized by early and asymptotic scaling regimes, separated by a crossover. The interplay among d

F. Piéchon M. Benakli, A. Jagannathan

We solve the approximate renormalisation group found by Qiu Niu and Franco Nori(Phys. Rev. Lett. 57 2057(1986)) for a tight-binding hamiltonian on the Fibonacci chain. This enables us to characterize analytically as completely as possible the spectral properties of this model, such as the spectral measure, the bandwidth distribution, the Lebesgue measure exp

Enzo Marinari, Giorgio Parisi, Felix Ritort

We study the statistical mechanics of a $D$-dimensional array of Josephson junctions in presence of a magnetic field on a lattice of side $2$. In the high temperature region the thermodynamical properties can be computed in the limit $D \to \infty$. A conjectural form of the thermodynamic properties in the low temperature phase is obtained by assuming that t

Michael R. Swift, W. R. Osborn, J. M. Yeomans

A lattice Boltzmann scheme able to model the hydrodynamics of phase separation and two-phase flow is described. Thermodynamic consistency is ensured by introducing a non-ideal pressure tensor directly into the collision operator. We also show how an external chemical potential can be used to supplement standard boundary conditions in order to investigate the

Michael A. Strauss, Jeffrey A. Willick

We review the quantitative science that can be and has been done with redshift and peculiar velocity surveys of galaxies in the nearby universe. After a brief background setting the cosmological context for this work, the first part of this review focuses on redshift surveys. The practical issues of how redshift surveys are carried out, and how one turns a d

A. Naim, O. Lahav, R. J. Buta, H. G. Corwin

We investigate the consistency of visual morphological classifications of galaxies by comparing classifications for 831 galaxies from six independent observers. The galaxies were classified on laser print copy images or on computer screen produced from scans with the Automated Plate Measuring (APM) machine. Classifications are compared using the Revised Hubb

Max Pettini, Keith Lipman, Richard W. Hunstead

The damped Lyman alpha systems seen in the spectra of high redshift QSOs offer the means to determine element abundances in galaxies observed while still at an early stage of evolution. Such measurements, which have only recently come within reach, complement and extend the data provided by studies of different stellar populations in our Galaxy and of extrag

Max Pettini, Richard W. Hunstead, David L. King, Linda J. Smith

We summarise the results of a deep search for Lyman alpha emission from star-forming regions associated with damped Lyman alpha absorption systems and conclude that the Lyman alpha luminosity of high redshift galaxies is generally less than 10^(42) erg/s . We also present a newly discovered case, in the field of the QSO Q2059-360, where the emission is unusu

A. D. King, P. E. Newstead

Let $\MS_g$ be the moduli space of stable holomorphic vector bundles of rank 2 and fixed determinant of odd degree over a smooth complex projective curve of genus $g$. This paper proves various properties of the rational cohomology ring $H^*(\MS_g)$. It is shown that the first relation in genus $g$ between the standard generators satisfies a recurrence relat

W. Barth, Th. Bauer

If there is one polygon inscribed into some smooth conic and circumscribed about another one, then there are infinitely many such polygons. This is Poncelet's theorem. The aim of this note is to collect some (mostly classical) versions of this theorem, namely: - Weyr's Poncelet theorem in $P_3$ (1870), - Emch's theorem on circular series (1901),

Niels Lauritzen

Let $G$ be a reductive linear algebraic group. The simplest example of a projective homogeneous $G$-variety in characteristic $p$, not isomorphic to a flag variety, is the divisor $x_0 y_0^p+x_1 y_1^p+x_2 y_2^p=0$ in $P^2\times P^2$, which is $SL_3$ modulo a non-reduced stabilizer containing the upper triangular matrices. In this paper embeddings of projecti

Boris Moishezon, Mina Teicher

We discuss the applications of fundamental groups (of complements of curves) computations (and possibly the computations of the second homotopy group as a model over it) to the classification of algebraic surface. We prove that the fundamental group of the complement of the branch curve of a generic projection of a Veronese surface to the complex plane is an

Atsushi Moriwaki

Let K be an algebraic number field and O_K the ring of integers of K. Let f : X --> Spec(O_K) be a stable arithmetic surface over O_K of genus g >= 2. In this short note, we will prove that if f has a reducible geometric fiber, then the self intersection of dualizing sheaf of X with Arakelov metric is greater than or equal to log(2)/6(g-1).

Jin-Xing Cai

This thesis is devoted to the study of abelian automorphism groups of surfaces and $3$-folds of general type over complex number field $\Bbb C$. We obtain a linear bound in $K^3$ for abelian automorphism groups of $3$-folds of general type whose canonical divisor $K$ is numerically effective, and we improve on Xiao's results on abelian automorphism group