We discover that the scaling property of the cosmology is synonymous with the scalar fields tracing out a particular class of geodesics in moduli space - those which are constructed as integral curves of the gradient of the log of the potential. Given a generic scalar potential we explicitly construct a moduli metric that allows scaling solutions, and we show the converse - how one can construct a potential that allows scaling once the moduli metric is known. We also ask what the origin of such cosmological scalars might be, and look to the scalars in the Kaluza-Klein compactification of higher-dimensional theories for a possible answer. Conventionally these scalars, or moduli fields, are required to be stabilised so that the gauge sector can be used to describe the field content of the standard model. Here we instead take the view that the scalar fields are dynamical moduli describing the squashings of an internal compactified manifold, and study the dynamics of such systems. We additionally consider the cosmological role of the scalar fields generated by the compactification of 11D Einstein gravity on a 7D elliptic twisted torus, which has the attractive features of giving rise to a positive semi-definite potential, and partially fixing the moduli. This compactification is therefore relevant for low energy M-theory, 11D supergravity. We find that there is no slow-roll inflation within a subclass of these twisted tori and give evidence that this result extends to a more general situation. Despite the lack of slow-roll, we find that there is a novel scaling solution in Friedmann cosmologies in which the massive moduli oscillate but maintain a constant energy density relative to the background barotropic fluid.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:487919 |
| Date | January 2007 |
| Creators | Karthauser, Josef |
| Publisher | University of Sussex |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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