August 1992 arXiv papers — page 3

M. D. Freeman, P. West

We establish a relation between the classical non-linear Schrödinger equation and the KP hierarchy, and we extend this relation to the quantum case by defining a quantum KP hierarchy. We present evidence that an integrable hierarchy of equations is obtained by quantizing the first Hamiltonian structure of the KdV equation. The connection between infinite-dim

I. I. Kogan, A. Morozov, G. W. Semenoff, N. Weiss

We investigate a class of operators with non-vanishing averages in a D-dimensional matrix model recently proposed by Kazakov and Migdal. Among the operators considered are ``filled Wilson loops" which are the most reasonable counterparts of Wilson loops in the conventional Wilson formulation of lattice QCD. The averages of interest are represented as par

Ahmed Ali, Thomas Mannel, Thorsten Ohl

We estimate the contributions of higher K-resonances to the radiative rare decays b -> s gamma. We use the spin symmetry for heavy quarks to reduce the number of independent form factors to four Isgur-Wise functions, which are estimated from the wave function model of Isgur, Scora, Grinstein, and Wise. Our results suggest a substantially larger branching fra

L. Xiong, E. Shuryak, G. E. Brown

Electromagnetic radiation from excited hadronic matter is one of the best ways to study the properties of the matter. Considering various processes in the hadronic gas, Kapusta et al \cite{Kapusta_photons} have found a $πρ\rightarrow πγ$ reaction with intermediate virtual pion or rho to be the main source of photons with energy greater than 0.7 GeV. However,

Alex Pomarol

We study the minimal version of the supersymmetric standard model with spontaneous CP breaking. In this model, the KM matrix is real and contributions to $\varepsilon$ arise from box diagrams involving squarks. We analyze the region of the parameter space which corresponds to values for $\varepsilon$, $\varepsilon^\prime/\varepsilon$ and the neutron electric

J. Bijnens, G. Ecker, J. Gasser

We present the matrix elements for the semileptonic kaon decays $K_{l2γ}$, $K_{l2l^+l^-}$, $K_{l2l'^+l'^-}$, $K_{l3}$, $K_{l3γ}$ and $K_{l4}$ at next-to-leading order in chiral perturbation theory and compare the predictions with experimental data. Monte Carlo event generators are used to calculate the corresponding rates at DAFNE. We discuss the pos

Xiao-Gang He, B. H. J. McKellar

We show that there is an anologous Aharonov-Casher effect on a neutral particle with electric dipole moment interacting with a magnetic filed produced by magnetic monopoles.

Marc Kamionkowski, Katherine Freese

Bubbles in a first-order electroweak phase transition are nucleated with radii $R_0$ and expand with velocity $v$. If $v$ is subsonic, a bubble becomes unstable to non-spherical perturbations when its radius is roughly $10^4\, R_0$. These perturbations accelerate the transition, and the effective velocity of bubble growth rapidly becomes supersonic. The tran

Toby Falk, Raghavan Rangarajan, Mark Srednicki

In the standard inflationary scenario with inflaton potential $V(Φ)=M^4-{1\over4}λΦ^4$, the resulting density perturbations $δρ/ρ$ are proportional to $λ^{1/2}$. Upper bounds on $δρ/ρ$ require $λ< 10^{-13}$. Ratra has shown that an alternative treatment of reheating results in $δρ/ρ\propto λ^{-1}$, so that an upper bound on $δρ/ρ$ does not put an obvious upp

Toby Falk, Raghavan Rangarajan, Mark Srednicki

Inflationary models predict a definite, model independent, angular dependence for the three-point correlation function of $ΔT/T$ at large angles (greater than $\sim 1^\circ$) which we calculate. The overall amplitude is model dependent and generically unobservably small, but may be large in some specific models. We compare our results with other models of no

Mike Flanigan, Pablo Tamayo

We present an algorithm for cluster dynamics to efficiently simulate large systems on MIMD parallel computers with large numbers of processors. The method divides physical space into rectangular cells which are assigned to processors and combines a serial local procedure with a nearest neighbor relaxation process. By controlling overhead and reducing inter-p

Shahn Majid

Braided groups and braided matrices are novel algebraic structures living in braided or quasitensor categories. As such they are a generalization of super-groups and super-matrices to the case of braid statistics. Here we construct braided group versions of the standard quantum groups $U_q(g)$. They have the same FRT generators $l^\pm$ but a matrix braided-c

Tomasz Brzezinski, Shahn Majid

We construct quantum group-valued canonical connections on quantum homogeneous spaces, including a q-deformed Dirac monopole on the quantum sphere of Podles quantum differential coming from the 3-D calculus of Woronowicz on $SU_q(2)$ . The construction is presented within the setting of a general theory of quantum principal bundles with quantum group (Hopf a

M. J. Martins

We introduce the A-D-E resonance factorized models as an appropriate analytical continuation of the Toda S-matrices to the complex values of their coupling constant. An investigation of the associated Casimir energy, via the thermodynamic Bethe ansatz, reveals a rich pattern of renormalization group trajectories interpolating between the central charges of t

Tomasz Brzezinski, Shahn Majid

We introduce a large class of bicovariant differential calculi on any quantum group $A$, associated to $Ad$-invariant elements. For example, the deformed trace element on $SL_q(2)$ recovers Woronowicz&#39; $4D_\pm$ calculus. More generally, we obtain a sequence of differential calculi on each quantum group $A(R)$, based on the theory of the corresponding bra

Jonathan M. Evans, Philip A. Tuckey

When a Hamiltonian system is subject to constraints which depend explicitly on time, difficulties can arise in attempting to reduce the system to its physical phase space. Specifically, it is non-trivial to restrict the system in such a way that one can find a Hamiltonian time-evolution equation involving the Dirac bracket. Using a geometrical formulation, w

Shahn Majid

Quantum matrices $A(R)$ are known for every $R$ matrix obeying the Quantum Yang-Baxter Equations. It is also known that these act on `vectors&#39; given by the corresponding Zamalodchikov algebra. We develop this interpretation in detail, distinguishing between two forms of this algebra, $V(R)$ (vectors) and $V^*(R)$ (covectors). $A(R)\to V(R_{21})\tens V^*(

S. Majid

Classical random walks and Markov processes are easily described by Hopf algebras. It is also known that groups and Hopf algebras (quantum groups) lead to classical and quantum diffusions. We study here the more primitive notion of a quantum random walk associated to a general Hopf algebra and show that it has a simple physical interpretation in quantum mech

J. C. Gaite

The field algebra of the minimal models of W-algebras is amenable to a very simple description as a polynomial algebra generated by few elementary fields, corresponding to order parameters. Using this description, the complete Landau-Ginzburg lagrangians for these models are obtained. Perturbing these lagrangians we can explore their phase diagrams, which co

M. Jamin, M. Muenz

The contributions to the coefficient functions of the quark and the mixed quark-gluon condensate to mesonic correlators are calculated for the first time to all orders in the quark masses, and to lowest order in the strong coupling constant. Existing results on the coefficient functions of the unit operator and the gluon condensate are reviewed. The proper f

F. Karsch, M. L. Laursen, T. Neuhaus, B. Plache

Using a variation of Lueschers geometric charge definition for SU(2) lattice gauge theory, we have managed to give a geometric expression for it&#39;s Chern-Simons ter. From this definition we have checked the periodic structure. we determined the Chern-Simons density for symmetric and asymmetric lattices near the critical region in the SU(2) Higgs model. Th

Michael J. Mehl

I have carried out numerical first principles calculations of the pressure dependence of the elastic moduli for several ordered structures in the Aluminum-Lithium system, specifically FCC Al, FCC and BCC Li, L1_2 Al_3Li, and an ordered FCC Al_7Li supercell. The calculations were performed using the full potential linear augmented plane wave method (LAPW) to

Subhashis Nag, Parameswaran Sankaran

An arbitrary Feynman graph for string field theory interactions is analysed and the homeomorphism type of the corresponding world sheet surface is completely determined even in the non-orientable cases. Algorithms are found to mechanically compute the topological characteristics of the resulting surface from the structure of the signed oriented graph. Whitne

David J. Gross

Migdal and Kazakov have suggested that lattice QCD with an adjoint representation scalar in the infinite coupling limit could induce QCD. I find an exact saddlepoint of this theory for infinite $N$ in the case of a quadratic scalar potential. I discuss some aspects of this solution and also show how the continuum D=1 matrix model with an arbitrary potential

I. Bars, K. Sfetsos

Pursuing further the recent methods in the algebraic Hamiltonian approach to gauged WZW models, we apply them to the bosonic SL(2,R) X SU(2)/R^2 model recently investigated by Nappi and Witten. We find the global space and compute the conformally exact metric and dilaton fields to all orders in the $1/k$ expansion. The semiclassical limit $k&#39;,k\to \infty

G. Iori, E. Marinari, G. Parisi

We study the dynamics of an heteropolymeric chain relaxing toward a new equilibrium configuration after the action of an external perturbation. We compare the results from Monte Carlo simulations with the results of a Langevin normal mode decomposition. We discuss, for sake of comparison, the case of an ordered homopolymeric chain.

J. Hisano, H. Murayama, T. Yanagida

We make a detailed analysis on the nucleon decay in the minimal supersymmetric $SU(5)$ grand unified model. We find that a requirement of the unification of three gauge coupling constants leads to a constraint on a mass $M_{H_C}$ of color-triplet Higgs multiplet as $2 \times 10^{13}~\GeV \leq M_{H_C} \leq 2 \times 10^{17}~\GeV$, taking both weak- and GUT-sca

Andreas Cap, Peter W. Michor

In this short review article we sketch some developments which should ultimately lead to the analogy of the Chern-Weil homomorphism for principal bundles in the realm of non-commutative differential geometry. Principal bundles there should have Hopf algebras as structure `cogroups&#39;. Since the usual machinery of Lie algebras, connection forms, etc\., just

Itzhak Bars

We explore the possibility of string theories in only four spacetime dimensions without any additional compactified dimensions. We show that, provided the theory is defined in curved spacetime that has a cosmological interpration, it is possible to construct consistent heterotic string theories based on a few non-compact current algebra cosets. We classify t