BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:An anisotropic\, non-singular early universe model leading to a re
 alistic cosmology - Pierre Dechant\, Cavendish Astrophysics
DTSTART:20081125T163000Z
DTEND:20081125T170000Z
UID:TALK13893@talks.cam.ac.uk
CONTACT:Jane Buckle
DESCRIPTION:We present a novel cosmological model in which scalar field ma
 tter in a biaxial Bianchi IX geometry leads to a non-singular `pancaking' 
 solution: the hypersurface volume goes to zero instantaneously at the Big 
 Bang\, but all physical quantities\, such as curvature invariants and the 
 matter energy density remain finite\, and continue smoothly through the Bi
 g Bang. We demonstrate that there exist geodesics extending through the Bi
 g Bang\, but that there are also incomplete geodesics that spiral infinite
 ly around a topologically closed spatial dimension at the Big Bang\, rende
 ring it\, at worst\, a quasi-regular singularity. The model is thus remini
 scent of the Taub-NUT vacuum solution in that it has biaxial Bianchi IX ge
 ometry and its evolution exhibits a dimensionality reduction at a quasi-re
 gular singularity\; the two models are\, however\, rather different\, as w
 e will show in a future work. Here we concentrate on the cosmological impl
 ications of our model and show how the scalar field drives both isotropisa
 tion and inflation\, thus raising the question of whether structure on the
  largest scales was laid down at a time when the universe was still oblate
  (as also suggested by Contaldi et al. We also discuss the stability of ou
 r model to small perturbations around biaxiality and draw an analogy with 
 cosmological perturbations. We conclude by presenting a separate\, bouncin
 g solution\, which generalises the known bouncing solution in closed FRW u
 niverses. 
LOCATION:Ryle Seminar Room\, Cavendish Laboratory
END:VEVENT
END:VCALENDAR