The Petrov classification and vacuum dark fluid

The Petrov classification of stress-energy tensors makes it possible to introduce a unified description of dark energy and dark matter as a vacuum dark fluid based on the space-time symmetry. In this approach a vacuum dark energy is described by a variable cosmological term whose symmetry is reduced as compared with the Einstein cosmological term which allows a vacuum energy to be evolving and clustering. The relevant class of solutions to the Einstein equations implies also the existence of compact vacuum objects generically related to a dark energy: regular black holes, their remnants and self-gravitating vacuum solitons with de Sitter vacuum interior – which can be responsible for observational effects typically related to a dark matter. The mass of objects with de Sitter interior is generically related to vacuum dark energy and to breaking of space-time symmetry.