Gr@v Seminar - Curvature perturbation in multi-field inflation models with non-minimal coupling - 26 fevereiro 2014



Curvature perturbation in multi-field inflation models with non-minimal coupling

Masato Minamitsuji

IST, Lisbon


Abstract / Resumo

Recent observations of the Cosmic Microwave Background (CMB) show very good consistency with an inflationary model with non-minimal coupling between the scalar and the inflaton field. Such a model is well motivated in the context of the unified theory, which also predicts the existence of many other scalar fields  in addition to the inflaton. Models with nonminimal coupling can be recast in the form of Einstein gravity via a conformal transformation.


Motivated by them, we study multi-field inflation models with nonminimal coupling. We focus on comparing the curvature perturbations associated with the Jordan and Einstein frames. The conformal transformation to the Einstein frame leads to additional couplings between fields that can potentially source non-Gaussianities. We are interested in how observables in the Einstein frame can be related back to those in the original Jordan frame. In the single-field case it is well known that they coincide to all orders of perturbation, but in the multi-field case this is no longer true. We discuss the relationship between the curvature perturbatons between two frames, highlighting that both the two quantities can potentially be different. After determining general expressions for the cosmological perturbations and associated spectra, we focus on some analytically soluble examples. We find that curvature perturbations in the Jordan and Einstein frames indeed evolve differently during inflation, but by the end of inflation they converge to the unique constant values interpreted as the final observables. The observables can easily be brought into agreement with the Planck results.


26 de fevereiro de 2014 | 15:00


Seminars webpage



GAP Room
Physics Department Aveiro University
Campus de Santiago
3810-183 Aveiro, Portugal