The Petrov algebraic classification and phase transitions in gravitational fields

This article shows the connection of the Petrov algebraic classification of gravitational fields with the theory of catastrophes as a generalized theory of phase transitions. We demonstrate the analogy between the transitions of the algebraic types of space-times and the phase transitions at the curvature tensor level (Weyl's matrices level) by the examples of the Petrov classification, the algebraic classification of four-dimensional local Euclidean spaces, and the derivation of the gravitational fields of lightlike sources.