| Speaker: | Hugo Holland (IAS) |
|---|---|
| Title: | The separate universe approach and gauge fixing procedures for multifield inflation models. |
| Date (JST): | Fri, Mar 13, 2026, 15:30 - 17:00 |
| Place: | Seminar Room A |
| Abstract: |
The separate universe approach (SUA) is a powerful tool offering us a simple way to compute cosmic inhomogeneities at large scales including their non-linear evolution. It consists in describing the universe as a collection of independent patches which are taken to be homogeneous and isotropic. The assumptions one has to do to apply the SUA and its simplifications need to be checked, notably in multifield models of inflation. In this talk I will present the validity conditions of the SUA in non-linear sigma models by matching it to a complete cosmological perturbation theory computation taken to large scales. In particular I will dive into the subtleties of gauge fixing procedures and how they compare in both schemes. I will then present ongoing efforts to proceed to a similar procedure beyond the leading order by considering third order hamiltonian dynamics. |
