Abstract

Relativistic generalisation of the Lenz vector (I) The non-relativistic motion of a particle in a central field with Mr potential, e.g. the motion of an electron in the Coulomb field of a charged nucleus at rest, is described by the equation of motion (non-relativistic Kepler problem) m x" = x • x /r\ with a = ez e (product of the charges of the central body ez and the electron e). From this equation of motion, three statements of con servation can be derived: in respect of the energy E, of the angular momentum L and of the Lenz vector A = m {jc' x L + x • x/r). The geometric meaning of A is that of a vector pointing in the direction of the perihelion of the particle orbits (conic sections). It will be demonstrated that also at the relativistic Kepler problem, which is based on the equation of motion m (jc'/|/T — (jc7c)2)' = x ■ x/r3 an analogous Lenz vector exists. It represents a quantity of conservation — in the same way as the relativistic energy and the relativistic angular momentum. For the transitional case — ► oo, where the relativistic problem turns into the non-relativistic problem, the relativistic Lenz vector also turns into the non-relativistic Lenz vector. The generalised (relativistic) Lenz vector has also a geometric meaning. Its direction coincides with the oriented axis of symmetry of the orbits (rosettes, spirals, hyperbola-type curves etc.). The quantity of conservation A occupies a special position in respect of the quantities of con servation energy and angular momentum. Whereas the energy and the angular momentum cor respond with a symmetry of time and space, the Lenz quantity of conservation corresponds with a symmetry of the orbits. The fact that the Lenz vector can relativistically be generalised touches thereby on principal aspects. R e la tiv is tis c h e V e r a llg e m e in e ru n g d e s L e n z s c h e n V e k to r s (I)