String Regge trajectory on de Sitter space and implications for inflation

by Toshifumi Noumi (Kobe)

Thursday 12 Dec 2019, 13:15 → 14:15 Europe/Stockholm

CoPS group room, A5:1041

I will discuss the spectrum of semiclassical rotating strings on de Sitter space and its consistency, generalizing the Gubser-Klebanov-Polyakov (GKP) string analysis on anti-de Sitter space. Even though a naive extrapolation of the linear Regge trajectory on flat space implies a violation of the Higuchi bound (a unitarity bound on the mass of higher-spin particles in de Sitter space), the curved space effects turn out to modify the trajectory to respect the bound. Interestingly, there exists a maximum spin for each Regge trajectory as a consequence of accelerated expansion, which is helpful to make the spectrum consistent with the Higuchi bound, but at the same time it could be an obstruction to stringy UV completion based on an infinite higher-spin tower. We discuss its possible implication for early universe inflation to motivate further studies in this direction.