We investigate the late-time asymptotics of future-expanding, polarized vacuum Einstein spacetimes
with
-symmetry
on
,
which, by definition, admit two spacelike Killing fields. Our main result is the
existence of a stable asymptotic regime within this class; that is, we provide here a
full description of the late-time asymptotics of the solutions to the Einstein equations
when the initial data set is close to the asymptotic regime. Our proof is based on
several energy functionals with lower-order corrections (as is standard for such
problems) and the derivation of a simplified model that we exhibit here. Roughly
speaking, the Einstein equations in the symmetry class under consideration consist of
a system of wave equations coupled to constraint equations plus a system of ordinary
differential equations. The unknowns involved in the system of ordinary
equations are blowing up in the future timelike directions. One of our main
contributions is the derivation of novel effective equations for suitably renormalized
unknowns. Interestingly, this renormalization is not performed with respect to a
fixed background, but does involve the energy of the coupled system of wave
equations. In addition, we construct an open set of initial data that are
arbitrarily close to the expected asymptotic behavior. We emphasize that, in
comparison, the class of Gowdy spacetimes exhibits a very different dynamical
behavior to the one we uncover in the present work for general polarized
-symmetric
spacetimes. Furthermore, all the conclusions of this paper are valid within the framework of
weakly
-symmetric
spacetimes previously introduced by the authors.
Keywords
Einstein equations, $T^2$-symmetry, future expanding
spacetime, late-time asymptotics, geodesic completeness
Laboratoire Jacques-Louis Lions and
Centre National de la Recherche Scientifique
Université Pierre et Marie Curie (Paris 6)
4 Place Jussieu
75252 Paris
France