Slow-roll corrections in multi-field inflation : a separate universes approach

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http://hdl.handle.net/10138/308366

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Karciauskas , M , Kohri , K , Mori , T & White , J 2018 , ' Slow-roll corrections in multi-field inflation : a separate universes approach ' , Journal of Cosmology and Astroparticle Physics , vol. 2018 , no. 5 , 021 . https://doi.org/10.1088/1475-7516/2018/05/021

Title: Slow-roll corrections in multi-field inflation : a separate universes approach
Author: Karciauskas, Mindaugas; Kohri, Kazunori; Mori, Taro; White, Jonathan
Contributor: University of Helsinki, Helsinki Institute of Physics
Date: 2018-05
Language: eng
Number of pages: 47
Belongs to series: Journal of Cosmology and Astroparticle Physics
ISSN: 1475-7516
URI: http://hdl.handle.net/10138/308366
Abstract: In view of cosmological parameters being measured to ever higher precision, theoretical predictions must also be computed to an equally high level of precision. In this work we investigate the impact on such predictions of relaxing some of the simplifying assumptions often used in these computations. In particular, we investigate the importance of slow-roll corrections in the computation of multi-field inflation observables, such as the amplitude of the scalar spectrum P-zeta, its spectral tilt n(s), the tensor-to-scalar ratio r and the non-Gaussianity parameter f(NL). To this end we use the separate universes approach and delta N formalism, which allows us to consider slow-roll corrections to the non-Gaussianity of the primordial curvature perturbation as well as corrections to its two-point statistics. In the context of the delta N expansion, we divide slow-roll corrections into two categories: those associated with calculating the correlation functions of the field perturbations on the initial flat hypersurface and those associated with determining the derivatives of the e-folding number with respect to the field values on the initial flat hypersurface. Using the results of Nakamura & Stewart '96, corrections of the first kind can be written in a compact form. Corrections of the second kind arise from using different levels of slow-roll approximation in solving for the super-horizon evolution, which in turn corresponds to using different levels of slow-roll approximation in the background equations of motion. We consider four different levels of approximation and apply the results to a few example models. The various approximations are also compared to exact numerical solutions.
Subject: cosmological perturbation theory
inflation
COSMOLOGICAL PERTURBATIONS
MULTICOMPONENT INFLATON
CONSTRAINTS
SPECTRUM
DYNAMICS
APPROXIMATION
GENERATION
EXPANSION
2ND-ORDER
CMB
114 Physical sciences
115 Astronomy, Space science
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