Exotic-singularity-driven dark energy

TL;DR

This paper explores various exotic singularities in cosmology, their physical implications, and how models with such singularities can account for dark energy, potentially occurring in the near future of the universe.

Contribution

It classifies different exotic singularities, relates them to physical theories, and demonstrates their viability as dark energy models using observational data.

Findings

Some exotic singularity models fit observational data as dark energy.

Certain singularities may occur in the near future of the universe.

Exotic singularities can violate energy conditions and influence cosmic evolution.

Abstract

We discuss various types of exotic (non-standard) singularities in the Universe: a Big-Rip (BR or type I), a Sudden Future Singularity (SFS or type II), a Generalized Sudden Future Singularity, a Finite Scale Factor singularity (FSF or type III), a Big-Separation (BS or type IV) and a $w$-singularity. They are characterized by violation of all or some of the energy conditions which results in a blow-up of all or some of the physical quantities: the scale factor, the energy density, the pressure, and the barotropic index. We relate the emergence of these singularities with physical theories (superstring, brane, higher-order gravity, loop quantum cosmology). We show how the models involving exotic singularities may serve as dark energy by applying the observational data. In particular, we show that some of these exotic singularities (though being of a weak type according to relativistic definitions) may occur in the near future of the universe.