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SUMMARY:An anisotropic\, non-singular early universe model leading to a re
 alistic cosmology - Pierre-Philippe Dechant (Cavendish)
DTSTART:20090119T130000Z
DTEND:20090119T140000Z
UID:TALK14596@talks.cam.ac.uk
CONTACT:Antony Lewis
DESCRIPTION:We present a novel cosmological model in which scalar field ma
 tter in\na biaxial Bianchi IX geometry leads to a non-singular `pancaking'
 \nsolution: the hypersurface volume goes to zero instantaneously at the\n`
 Big Bang'\, but all physical quantities\, such as curvature invariants\nan
 d the matter energy density remain finite\, and continue smoothly\nthrough
  the Big Bang.\nWe demonstrate that there exist geodesics extending throug
 h the Big\nBang\, but that there are also incomplete geodesics that\nspira
 l infinitely around a topologically closed spatial dimension at\nthe Big B
 ang\, rendering it\, at worst\, a quasi-regular singularity. The\nmodel is
  thus reminiscent of the Taub-NUT vacuum solution in that it has  biaxial 
 Bianchi IX geometry\nand its evolution exhibits a dimensionality reduction
  at a quasi-regular\nsingularity\; the two models are\, however\, rather d
 ifferent\, as we will\nshow in a future work.  Here we concentrate on the 
 cosmological\nimplications of our model and show how the scalar field driv
 es both\nisotropisation and inflation\, thus raising the question of wheth
 er\nstructure on the largest scales was laid down at a time when the\nuniv
 erse was still oblate (as also suggested by\nPitrou et al and Contaldi et 
 al).  We also\ndiscuss the stability of our model to small perturbations a
 round\nbiaxiality and draw an analogy with cosmological perturbations. We\
 nconclude by presenting a separate\, bouncing solution\, which\ngeneralise
 s the known bouncing solution in closed FRW universes.
LOCATION:CMS\, Pav.B\, First Floor Common Room (B1.19)
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