On the Bel radiative gravitational fields

TL;DR

This paper classifies radiative gravitational fields into three types based on Bel's framework, linking them to physical situations, and introduces concepts like observer at rest and proper super-energy, analyzing inequalities related to super-energy.

Contribution

It provides a detailed classification of Bel radiative gravitational fields and introduces the concepts of observer at rest and proper super-energy in this context.

Findings

Three radiative types correspond to different physical situations.

Proper super-energy is minimized for non radiative fields by observers at rest.

Several super-energy inequalities are examined.

Abstract

We analyze the concept of intrinsic radiative gravitational fields defined by Bel and we show that the three radiative types, N, III and II, correspond with the three following different physical situations: {\it pure radiation}, {\it asymptotic pure radiation} and {\it generic} (non pure, non asymptotic pure) {\it radiation}. We introduce the concept of {\em observer at rest} with respect to the gravitational field and that of {\em proper super-energy} of the gravitational field and we show that, for non radiative fields, the minimum value of the relative super-energy density is the proper super-energy density, which is acquired by the observers at rest with respect to the field. Several {\it super-energy inequalities} are also examined.