Modern Physics Letters A

We present new higher-dimensional anisotropic cosmological solutions of gravity theories with Gauss-Bonnet terms. We establish the existence of inflationary models of the extended de Sitter types in this approach. An algorithm to find perfect fluid solutions from known “seed” solutions is given.

The classical evolution in the modified Starobinsky model, which is essentially a higherderivative theory with a Lagrangian density L~R+αR², has been studied right from thePlanck time , when the universe had emerged out of the quantum foam. The modelis known to admit an inflationary solution, but we have noted an initial stage of evolutionwith very interesting features. If the scalaron mass is small, M~10⁻⁵M_p, and the initialvalue of the scalar curvature, R₀≫M², both R and H approach some asymptotic values.Thus the subsequent evolution is almost insensitive to the initial values of R or H chosen,and depends only on an undetermined integration constant, which determines theseasymptotic values. An analytic expression connecting t, the age of the universe, and H(t) has been obtained. Results for the later stages in the evolution generally agree with thoseobtained recently by some other authors.

In nuclear collisions of Au+Au, Nb+Nb and Ca+Ca at bombarding energies between 150 and 800 MeV per nucleon, transverse energy and transverse momenta of light particles are studied event by event at θ=90° in the center of mass system. At all energies, a rise of the mean transverse energy per nucleon is observed with increasing charged particle multiplicity. Particularly large values of E_⊥ have been found for ³He-fragments. The hydrodynamical picture is discussed for a possible separation of the collective flow and the thermal parts of the E_⊥-spectrum. From this, evidence for a rather stiff equation of state is found.

The free Schrödinger equation for multipole degrees of freedom is linearized so that energy and momentum operators appear only in first order. As an example, we demonstrate the linearization procedure for quadrupole degrees of freedom. The wave function solving this equation carries a spin. We derive the operator of the collective spin and its eigenvalues depending on multipolarity.

Superstring inspired models contain, in general, extra quarks per family beyond those of the standard model. These quarks may give considerable contributions to b→sγ. Limits on their masses and couplings may be extracted from the presently available upper limits on this rare decay.

The energy dependence of the low-energy weak elastic proton-proton asymmetry in the Hybrid Quark Hadron model is opposite to that in conventional hadronic models. This can provide a test for quark cluster vs conventional models of short-range nuclear structure and reactions.

We present an analysis of possible infinities that may be present in uncompactified multi-loop heterotic and type II superstring amplitudes constructed, without use of the short-string limit, in the light-cone gauge, and with use of a closed [10]-SUSY field theory algebra. Various types of degenerations of the integrand are discussed on the string world-sheet. No infinities are found, modulo (for type II) a particular identity for Green’s functions.

We have derived the quantum mechanical versions of infinite number of conservation laws associated with Derivative Nonlinear Schrödinger equation with the help of a methodology used in string theory. The renormalised version of the conserved quantities are obtained with explicit forms of the counter terms.

We propose an algebraic method to determine anomalous commutators, which constitute Faddeev’s anomaly, for general dimensions. This method is verified explicitly in 1+5 dimensions.

In the framework of a diquark model of the nucleon, the strong scaling violation of the p/π⁺-ratio in the pp-collisions from (IHEP, Serpukhov) to (FNAL) and to (CERN ISR) is described. A fairly good description of the magnitude of cross sections for single protons and for symmetric-proton-pairs with large-p_⊥ is obtained. In the model with the dominating scalar (ud)-diquark, the yield relation Λ⁰/p≃K⁺/π⁺ is predicted.

Linear gravitons and spin-two gauge invariance appear in several places in string theories. The purpose of this note is to clarify the connection between gravitons which are emitted by vertex operators in conformal field theories and those which appear in conformally invariant sigma models, and to compare the associated gauge invariances. The polarization tensor and scalar field of a graviton-dilaton vertex are shown to obey equations of motion which are identical to the sigma model equations of motion if, and only if, the trace of the polarization tensor is massless. The gauge invariance of this vertex is a restricted version of the normal spin-two gauge invariance, but is seen to be sufficient to imply conservation of spacetime stress energy of the string.