Gravitoelectromagnetism

Gravitoelectromagnetism is briefly reviewed and some recent developments in this topic are discussed. The stress-energy content of the gravitoelectromagnetic field is described from different standpoints. In particular, the gravitational Poynting flux is analyzed and it is shown that there exists a steady flow of gravitational energy circulating around a rotating mass.Comment: LaTeX file, no figures, 12 pages, Plenary talk given at EREs2000 (Valladolid, Spain, 6-9 September 2000); to be published in Proc. Spanish Relativity Meeting, edited by J.-F. Pascual-S\'anchez, L. Flor\'ia, A. San Miguel, and F. Vicente (World Scientific, 2001

On the spin-rotation-gravity coupling

The inertial and gravitational properties of intrinsic spin are discussed and some of the recent work in this area is briefly reviewed. The extension of relativistic wave equations to accelerated systems and gravitational fields is critically examined. A nonlocal theory of accelerated observers is presented and its predictions are compared with observation.Comment: LaTeX, 13 pages, no figures. Submitted to Hehl festschrift (GRG, to appear

Nonlocal Transformations for Accelerated Observers

According to the locality postulate of special relativity, the measurements of physical fields by accelerated observers at a given event in Minkowski spacetime are related to each other by the representations of the Lorentz group. Nonlocal extensions of these representations are necessary, however, once acceleration-induced nonlocality is taken into account. The particular case of Dirac spinors is treated in detail and the corresponding nonlocal transformation group is studied.Comment: 8 pages, accepted for publication in Ann. Phys. (Berlin

Gravitation and Nonlocality

The physical basis of the standard theory of general relativity is examined and a nonlocal theory of accelerated observers is described that involves a natural generalization of the hypothesis of locality. The nonlocal theory is confronted with experiment via an indirect approach. The implications of the results for gravitation are briefly discussed.Comment: LaTeX file, no figures, 12 pages. To be published in: Proc. 25th Johns Hopkins Workshop "2001: A Relativistic Spacetime Odyssey" (World Scientific, Singapore

General formulation of Luria-Delbr{\"u}ck distribution of the number of mutants

The Luria-Delbr{\"u}ck experiment is a cornerstone of evolutionary theory, demonstrating the randomness of mutations before selection. The distribution of the number of mutants in this experiment has been the subject of intense investigation during the last 70 years. Despite this considerable effort, most of the results have been obtained under the assumption of constant growth rate, which is far from the experimental condition. We derive here the properties of this distribution for arbitrary growth function, for both the deterministic and stochastic growth of the mutants. The derivation we propose uses the number of wild type bacteria as the independent variable instead of time. The derivation is surprisingly simple and versatile, allowing many generalizations to be taken easily into account