Rotating 5D-Kaluza-Klein Space-Times from Invariant Transformations

Using invariant transformations of the five-dimensional Kaluza-Klein (KK) field equations, we find a series of formulae to derive axial symmetric stationary exact solutions of the KK theory starting from static ones. The procedure presented in this work allows to derive new exact solutions up to very simple integrations. Among other results, we find exact rotating solutions containing magnetic monopoles, dipoles, quadripoles, etc., coupled to scalar and to gravitational multipole fields.Comment: 24 pages, latex, no figures. To appear in Gen. Rel. Grav., 32, (2000), in pres

Nonlinear Analysis of Thin Fracture Specimens Using Solid, Isoparametric Finite Elements

This report examines the performance of various "solid" finite elements for the analysis of thin shell structures often encountered in nonlinear fracture mechanics studies. Such models require solid elements in the crack front region to capture strong through-thickness effects; modeling of the entire test specimen-structural element with solid elements then proves convenient. Unfortunately, the standard 8-node "brick" element with full integration exhibits strong shear-locking under bending deformations and thus overly stiff behavior. Three alternative elements are examined here: the 8-node element with single-point integration, the 8-node element with enhanced (incompatible) modes and the 20-node (quadratic) element. Element performance is assessed through analyses of a thin M(T) fracture specimen loaded in remote tension. This specimen generates strong compressive (T- )stresses parallel to the crack growth direction which leads to out-of-plane bending in the crack front region (triggered by a small normal force). The displacements obtained with a refined mesh of thin shell elements provide the reference solution for evaluation of the solid element performance. The analyses include large-displacement effects, but linear material response for simplicity, and are performed with Abaqus 5.6 and Warp3D. The results show clearly that both the 8-node element with enhanced modes and the 20-node element with conventional reduced integration provide solutions of accuracy comparable to the thin shell element. Mixed 8 and 20-node element meshes for ductile fracture analyses with transition elements to maintain displacement compatibility are demonstrated to provide an accurate and efficient modeling strategy.NASA-AMES Research CenterNASA-Langley Research CenterContract Nos. NCC 2-5126 and NAG 2-112

Class of Einstein--Maxwell Dilatons

Three different classes of static solutions of the Einstein--Maxwell equations non--minimally coupled to a dilaton field are presented. The solutions are given in general in terms of two arbitrary harmonic functions and involve among others an arbitrary parameter which determines their applicability as charged black holes, dilaton black holes or strings. Most of the known solutions are contained as special cases and can be non--trivially generalized in different ways.Comment: Published in Physical Review D, R310 (1995

Solutions in Self-Dual Gravity Constructed Via Chiral Equations

The chiral model for self-dual gravity given by Husain in the context of the chiral equations approach is discussed. A Lie algebra corresponding to a finite dimensional subgroup of the group of symplectic diffeomorphisms is found, and then use for expanding the Lie algebra valued connections associated with the chiral model. The self-dual metric can be explicitly given in terms of harmonic maps and in terms of a basis of this subalgebra.Comment: Plain Latex, 13 Pages, major revisions of style in the above proof, several Comments added. Version to appear in Physical Review

Revivals, collapses and magnetic-pulse generation in quantum rings

Using a microscopic theory based on the density matrix formalism we investigate quantum revivals and collapses of the charge polarization and charge current dynamics in mesoscopic rings driven by short asymmetric electromagnetic pulses. The collapsed state is utilized for sub-picosecond switching of the current and associated magnetization, enabling thus the generation of pulsed magnetic fields with a tunable time structure and shape asymmetry which provides a new tool to study ultrafast spin-dynamics and ratchet-based effects.Comment: 4 pages, 2 figure