Hidden-sector fermions in two or three generations

TL;DR

This paper discusses how sterile fermions, called sterinos, naturally appear in two or three generations due to fundamental principles, and explores their potential role as dark matter candidates in cosmology.

Contribution

It introduces a theoretical argument based on Dirac's procedure and Pauli principle explaining the generation structure of sterile fermions and links them to dark matter models.

Findings

Sterinos are predicted to appear in two or three generations.

Stable sterinos could account for cold dark matter.

Exciting cold dark matter may form if sterinos are only stable in the lowest generation.

Abstract

We recall the argument based both on Dirac's square root procedure and an intrinsic Pauli principle that sterile fundamental fermions with spin 1/2 (sterinos) ought to appear in Nature in two or three generations, while the Standard Model leptons and quarks are forced to develop three generations. Then, sterinos in two or three generations, if stable, lead to the cold dark matter in two or three species, when the thermal freeze-out mechanism works properly. If they are stable only in their lowest generation, the so called exciting cold dark matter may be formed.