Predictions in multifield inflation

Frazer, Jonathan (2013) Predictions in multifield inflation. Doctoral thesis (PhD), University of Sussex.

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Abstract

Models of inflation with more than one active field are an important class where it is not fully understood how to compute predictions. This problem can be understood in
terms of two characteristics of these models: the sensitivity to initial conditions and the superhorizon evolution of the primordial density perturbation ζ. This thesis seeks to make significant progress in understanding how to overcome these two issues.

To track the superhorizon evolution of ζ in general requires numerical techniques. By extending the transport method first proposed by Mulryne, Seery and Wesley, here, a
computationally efficient and highly versatile method for computing the statistics of ζ is developed. The increased efficiency and versatility allows models that were previously unaccessible to be studied.

Utilising this new capability two models are explored. A new toy model of inflation in the Landscape and a 6-field D-brane model of inflation first proposed by Agarwal,
Bean, McAllister, and Xu. The nature of these models allows for a statistical analysis of inflationary realisations to be performed. We conclude that the fundamental ability to
constrain models of this kind is determined by the scale of features in the potential. We also show the D-brane model is under considerable pressure from current observations of
the spectral index and may be ruled out by future observations.

Finally, I show that there exists a class of models for which the probability distribution of observables may be computed analytically. I show the peak of the density function is largely dominated by the geometry of the potential and comparatively insensitive to the distribution of initial conditions. I argue that this characteristic should be expected in a broader range of models and for such models, it is possible to make robust predictions.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QB Astronomy > QB0980 Cosmogony. Cosmology
Depositing User: Library Cataloguing
Date Deposited: 11 Oct 2013 06:26
Last Modified: 17 Sep 2015 12:07
URI: http://srodev.sussex.ac.uk/id/eprint/46616

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