"Vacuum-like" Hadamard states for quantum fields on curved spacetimes

Understand

We present a modification of the recently proposed Sorkin-Johnston states for scalar free quantum fields on a class of globally hyperbolic spacetimes possessing compact Cauchy hypersurfaces.

• The modification relies on a smooth cutoff of the commutator function and leads always to Hadamard states, in contrast to the original Sorkin-Johnston states.
• The modified Sorkin-Johnston states are, however, due to the smoothing no longer uniquely associated to the spacetime.