Four-force

About: Four-force is a research topic. Over the lifetime, 3459 publications have been published within this topic receiving 87308 citations.

The birth of special relativity. "One more essay on the subject"

Abstract: Special relativity was discovered at the eve of the century, but finds its roots in the 19th century efforts to understand the optics and electromagnetism of moving bodies. These roots are reviewed in Parts 1 and 2, the latter being specially devoted to the works of Lorentz and of Poincare up to 1904. Part 3 contains a detailed comparison of the works of Einstein and of Poincare in 1905. It is shown that both authors succeeded in constructing a coherent and fully relativistic theory, although their ideas about the ether were radically different. In Part 4, the question of the respective merits of the three potential fathers of special relativity (i.e. Lorentz, Poincare, Einstein) is discussed again, at the light of the preceding analysis and of the "post-1905" developments of the theory.

Special relativity and the flow of time

Abstract: N. Maxwell (1985) has claimed that special relativity and "probabilism" are incompatible; "probabilism" he defines as the doctrine that "the universe is such that, at any instant, there is only one past but many alternative possible futures". Thus defined, the doctrine is evidently prerelativistic as it depends on the notion of a universal instant of the universe. In this note I show, however, that there is a straightforward relativistic generalization, and that therefore Maxwell's conclusion that the special theory of relativity should be amended is unwarranted. I leave open the question whether or not probabilism (or the related doctrine of the flow of time) is true, but argue that the special theory of relativity has no fundamental significance for this question.

Particle decay in six-dimensional relativity

Abstract: Special relativity is developed using a real six-dimensional space-time. It is shown that the imposition of parallel time displacements in each frame necessarily implies subluminal transformations. Conservation of six-momentum yields the usual three-momentum equation together with a vector equation, which replaces the scalar energy equation of the corresponding four-dimensional theory. On energetic grounds alone it is shown that a particle may decay into a set of particles whose total rest mass is greater than that of the original particle, and that particles may be produced from the vacuum state. When virtual particle production is considered, this suggests a tentative link between the uncertainty principle and a six-dimensional theory with a restriction to small deviations from a constant time direction.

Construction of initial data for 3+1 numerical relativity

Abstract: This lecture is devoted to the problem of computing initial data for the Cauchy problem of 3+1 general relativity. The main task is to solve the constraint equations. The conformal technique, introduced by Lichnerowicz and enhanced by York, is presented. Two standard methods, the conformal transverse-traceless one and the conformal thin sandwich, are discussed and illustrated by some simple examples. Finally a short review regarding initial data for binary systems (black holes and neutron stars) is given.

An introduction to the general theory of relativity

Abstract: Fundamental aspects of general relativity are considered, with special emphasis on cosmological problems. Points of disagreement between special and general relativity are discussed. Subjects investigated include rotating coordinate systems, the equivalence principle, tensor analysis, Riemannian geometry, the Schwarzschild and Einstein fields, and Mach's principle. (T.F.H.)