Brane inflation, solitons and cosmological solutions: I

In this paper we study various cosmological solutions for a D3/D7 systemdirectly from M-theory with fluxes and M2-branes. In M-theory, these solutionsexist only if we incorporate higher derivative corrections from the curvaturesas well as G-fluxes. We take these corrections into account and study a numberof toy cosmologies, including one with a novel background for the D3/D7 systemwhose supergravity solution can be completely determined. This new backgroundpreserves all the good properties of the original model and opens up avenues toinvestigate cosmological effects from wrapped branes and brane-antibraneannihilation, to name a few. We also discuss in some detail semilocal defectswith higher global symmetries, for example exceptional ones, that could occurin a slightly different regime of our D3/D7 model. We show that the D3/D7system does have the required ingredients to realise these configurations asnon-topological solitons of the theory. These constructions also allow us togive a physical meaning to the existence of certain underlying homogeneousquaternionic Kahler manifolds.Comment: Harvmac, 115 pages, 9 .eps figures; v2: typos corrected, references added and the last section expanded; v3: Few minor typos corrected and references added. Final version to appear in JHE