Talk detail

Participant	Clifton, Timothy
Institution	Queen Mary University of London - Mile End Road - London - London - United Kingdom

Session	DE2	Accepted		Order	Time
Talk	Oral abstract	Title	What's The Matter In Cosmology?
Coauthors
Abstract	Almost all models of the universe start by assuming that matter fields can be modelled as dust. In the real universe, however, matter is clumped into dense objects that are separated by regions of space that are almost empty. If we are to treat such a distribution of matter as being modelled as a fluid, in some average or coarse-grained sense, then there a number of questions that must be answered. One of the most fundamental of these is whether or not the interaction energy between masses should gravitate. If it does, then a dust-like description may not be sufficient. We would then need to ask how interaction energies should be calculated in cosmology, and how should they appear in the Friedmann-like equations that govern the large-scale behaviour of the universe? I will discuss some recent results that may shed light on these questions.
Pdf file

Session	AT1	Accepted		Order	Time
Talk	Oral abstract	Title	Embedding Non-Linear Structures In f(R) Cosmologies
Coauthors
Abstract	When using Einstein's equations, there exist a number of techniques for embedding non-linear structures in cosmological backgrounds. These include Swiss cheese models, in which spherically symmetric vacua are patched onto Friedmann solutions, and lattice models, in which weak-field regions are joined together directly. In this talk we will consider how these methods work in f(R) theories of gravity. We will show that their existence places constraints on the large-scale expansion of the universe, and that it may not always be possible to consider the Friedmann solutions and weak-field solutions of a theory independently from each other.
Pdf file