Creation of Matter in the Universe and Groups of Type E7

TL;DR

This paper links matter creation after inflation to a universal property of extended supergravities, showing that scalar-vector couplings essential for matter generation are inherent in these models due to their mathematical structure.

Contribution

It demonstrates that nonminimal scalar-vector couplings, crucial for matter creation, are a universal feature of extended supergravities with symmetric coset spaces, providing a new theoretical insight.

Findings

Scalar-vector coupling is universal in extended supergravities.

This coupling is essential for matter creation in early universe models.

Most models preserve this coupling upon truncation, except specific cases.

Abstract

We relate the mechanism of matter creation in the universe after inflation to a simple and universal mathematical property of extended N > 1 supergravities and related compactifications of superstring theory. We show that in all such models, the inflaton field may decay into vector fields due to a nonminimal scalar-vector coupling. This coupling is compulsory for all scalars except N=2 hyperscalars. The proof is based on the fact that all extended supergravities described by symmetric coset spaces G/H have duality groups G of type E7, with exception of U(p,n) models. For N=2 we prove separately that special geometry requires a non-minimal scalar-vector coupling. Upon truncation to N=1 supergravity, extended models generically preserve the non-minimal scalar-vector coupling, with exception of U(p,n) models and hyperscalars. For some string theory/supergravity inflationary models, this coupling provides the only way to complete the process of creation of matter in the early universe.