Mr Christopher Sean Gallagher
Email: email@example.comRoom Number: G. O. Jones Building, Room 504
1st Supervisor: Dr Timothy Clifton
2nd Supervisor: Dr Chris Clarkson
Project Title: Relativistic Foundations of Cosmology.
I work on non-standard perturbation theory techniques within the context of general relativity in the cosmological setting. Specifically, I am working on applying perturbation theory on two scales using a two parameter expansion, using post-Newtonian theory to model fluctuations on short scales and standard cosmological perturbation theory to model fluctuations on large scales. Such expansions have not been tackled in the literature, yet they bear resemblance to some of the counting schemes such as the “weak field expansion”, and certain limits of second order cosmological perturbation theory. Intriguingly though, the existence of a two parameter gauge transformation mandates the inclusion of “mixed” terms that contain fluctuations on both scales and are sourced by both post-Newtonian and cosmological terms.
These indicate the existence of previously unexamined relativistic effects due to the interplay of different length scales, effects that may be measurable in upcoming galaxy surveys. We hope that this exciting new approach to precision cosmological modelling may enable us to further constrain general relativity (and it’s alternatives) in the cosmological setting - one of the great tasks in physics for the next thirty years.
Examples of research funding:
Science and Technology Facilities Council (STFC)
Perturbation theory for cosmologies with non-linear structure, Sophia R. Goldberg, Christopher Gallagher, Timothy Clifton. https://arxiv.org/abs/1707.01042