Quantum fluctuations during cosmic inflation

Cosmological inflation describes an accelerated expansion of the Universe at ultra-high energies in the very early universe. It is the simplest explanation for the large-scale homogeneity and isotropy of our Universe but, crucially, it also generates primordial density perturbations which go on to form the large-scale structure of our universe. Small-scale quantum field fluctuations during inflation are swept up by the rapid expansion to astronomical scales. Primordial perturbations produced by inflation are thus a probe of the effective field theory and different particle species at ultra-high energies.

This project will explore inflationary dynamics in different theoretical models and the generation of primordial perturbations. We will investigate how the statistical properties of perturbations in the cosmic microwave background and large-scale galaxy surveys are sensitive to the particle physics theory. In particular we will consider the imprint of higher spin fields in the scalar (density) and tensor (gravitational wave) power spectra and higher-order correlators and cross-correlations. We will also consider the role that long-wavelength quantum fluctuations play in the stochastic distribution of field values during inflation on scales even beyond our observable horizon. Ultimately our aim is to make quantitative statistical comparisons of the evidence for different theoretical models of inflation.