On space-times admitting shear-free, irrotational, geodesic null congruences

TL;DR

This paper investigates specific space-times in general relativity that feature shear-free, irrotational, geodesic null congruences, focusing on cases where the gravitational field combines perfect fluid and null radiation effects.

Contribution

It provides a detailed analysis of such space-times, highlighting their properties and the conditions under which they occur, expanding understanding of their structure in Einstein's theory.

Findings

Characterization of space-times with shear-free, irrotational, geodesic null congruences.

Conditions for the coexistence of perfect fluid and null radiation in these space-times.

Insights into the geometric and physical properties of these solutions.

Abstract

Space-times admitting a shear-free, irrotational, geodesic null congruence are studied. Attention is focused on those space-times in which the gravitational field is a combination of a perfect fluid and null radiation.