Running of scalar spectral index in multi-field inflation

Abstract

We compute the running of the scalar spectral index in general multi-field slow-roll inflation. By incorporating explicit momentum dependence at the moment of horizon crossing, we can find the running straightforwardly. At the same time, we can distinguish the contributions from the quasi de Sitter background and the super-horizon evolution of the field fluctuations.

Comments: (v1) 7 pages; (v2) 8 pages, 1 figure, discussions expanded especially regarding the initial conditions, to appear in Journal of Cosmology and Astroparticle Physics