The Theory of Causal Fermion Systems

The present universe contains more matter than antimatter. It is an open problem of contemporary physics to explain how the magnitude of the predominance of matter comes about. Moreover, one needs to identify and quantify the underlying physical effects. One scenario is that there was no predominance of matter right after the big bang, and that the matter/anti-matter asymmetry was generated dynamically.
This scenario is usually referred to as baryogenesis.

In [FJP21] it is shown that the theory of causal fermion systems gives rise to a novel mechanism of baryogenesis. Our mechanism falls into the category of fermiogenesis, with the asymmetry occurring in the same way for leptons and quarks, thereby guaranteeing for the matter content to be neutral with respect to all charges.

Our mechanism is based on the fact that in the theory of causal fermion systems the concept of the Dirac sea is implemented literally, with an ultraviolet regularization. The key point is that in the presence of gravitational fields, the regularization length as well as the detailed form of the regularization of the causal fermion system changes dynamically. This also means that the number of states per spatial volume needed to form a regularized Dirac sea configuration may change in time. On the other hand, the number of states per spatial volume is determined by current conservation as expressed by a conserved surface layer integral. Combining these results, one finds that, as time evolves, there should be an “excess” or “shortage” of states to fill the Dirac sea. If this is the case, either we have physical wave functions “left over” which must occupy particle states, or else there will remain “holes” in the Dirac sea describing anti-particles. Therefore, in the effective description of the causal fermion system in familiar language, the system will evolve from a vacuum spacetime to a spacetime with a matter/anti-matter asymmetry.

First ideas for possible applications to cosmology are given in [Pa18]. The detailed physical consequences are presently under investigation.
→ The matter/anti-matter asymmetry in current resarch projects