Talk detail

Participant	Cotsakis, Spiros
Institution	University of the Aegean - 3, Anat. Romilias Str - Athens - Papagos - Greece

Session	GT2	Accepted		Order	Time
Talk	Oral abstract	Title	Sudden movable singularities
Co-authors
Abstract	We study the structure of cosmological space-times in the vicinity of a sudden singularity. FRW solutions with a sudden singularity in the standard form usually defined in the literature cannot be general ones, and this poses the question of whether there exist any cosmological solutions having the qualitative features of a sudden singularity and the right number of arbitrary constants to qualify as general solutions of the field equations. We construct, via an asymptotic argument, the general form of a solution of this sort and show that such solutions cannot be uniformized (so that geodesics are now not well defined at the sudden singularity) in complete distinction with the sudden ¡singularities¢ read directly out of the form of the geodesic equations. This raises in turn a more general issue about the definition of singularities in the form geodesic incompleteness.

Session	GT2	Accepted		Order	Time
Talk	Oral abstract	Title	Structure of infinity in cosmology
Co-authors
Abstract	We extend Poincare's central extension method, which analyzes the behaviour at infinity, to cover weight-homogeneous vector fields and singularities which are situated at a finite rather than infinite time away. We apply this extension to a number of example cases in homogeneous and isotropic cosmology and show how one may treat the dynamics near finite equilibria and those at infinity in a unified way. We also provide evidence of how this extension is related to structural stability.