1201.6070 (Vladimir Chernov et al.)

Smooth cosmic censorship    [PDF]

Vladimir Chernov, Stefan Nemirovski

It is observed that on many 4-manifolds there is a unique smooth structure
underlying a globally hyperbolic Lorentz metric. For instance, every
contractible smooth 4-manifold admitting a globally hyperbolic Lorentz metric
is diffeomorphic to the standard $\R^4$. Similarly, a smooth 4-manifold
homeomorphic to the product of a closed oriented 3-manifold $N$ and $\R$ and
admitting a globally hyperbolic Lorentz metric is in fact diffeomorphic to
$N\times \R$. Thus one may speak of a censorship imposed by the global
hyperbolicty assumption on the possible smooth structures on
$(3+1)$-dimensional spacetimes.

View original: http://arxiv.org/abs/1201.6070