Theory HEP Seminar

Inflation from spontaneously broken Weyl invariance in theories with torsion

Stefano Lucat

Utrecht U.

Introduction of the torsion tensor on the space-time manifold leads to a Weyl invariant geometry, in which the torsion trace acts as a “U(1)” compensating field for the conformal transformations. Such symmetry can be extended to the whole matter sector included in the standard model by coupling the Higgs scalar (and all other possible fundamental scalars) to the torsion. A relevant question is then whether such framework can be used to describe cosmic inflation, as a spontaneous symmetry breaking phenomenon. It turns out that this is indeed possible because the Weyl invariance imposes a distinct field space geometry, which introduces a slow roll plateau in the otherwise too steep quartic potential dictated by Weyl symmetry. The model can have observable consequences that distinguish it from other inflationary scenarios, at least under some choices of initial conditions.