Thursday, March 29, 2012

1203.6125 (Helmut Friedrich)

Conformal structures of static vacuum data    [PDF]

Helmut Friedrich
In the Cauchy problem for asymptotically flat vacuum data the solution-jets along the cylinder at space-like infinity develop in general logarithmic singularities at the critical sets at which the cylinder touches future/past null infinity. The tendency of these singularities to spread along the null generators of null infinity obstructs the development of a smooth conformal structure at null infinity. For the solution-jets arising from time reflection symmetric data to extend smoothly to the critical sets it is {\it necessary} that the Cotton tensor of $h$ satisfies a certain conformally invariant condition at space-like infinity, it is {\it sufficient} that the initial three-metric $h$ be asymptotically static at space-like infinity. The purpose of this article is to characterize the possible gap between these conditions. We show that with the class of metrics which satisfy the first condition and a certain non-degeneracy requirement is associated a one-form $\kappa$ with conformally invariant differential $d\kappa$ which allows us to formulate a criterion under which $h$ is asymptotically conformal to static data at space-like infinity. With the understanding presently available, showing that smoothness at the critical sets implies this criterion amounts essentially to showing that necessary and sufficient for the solution-jets to be smooth at the critical sets is that the initial metric $h$ behaves at space-like infinity asymptotically like static data.
View original: http://arxiv.org/abs/1203.6125

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