Ori-Soen time machine - art. no. 124022

Ori and Seen have proposed a spacetime which has closed causal curves on th e boundary of a region of normal causality, all within a region where the w eak energy condition (positive energy density) is satisfied. I analyze the causal structure of this spacetime in some simplified models, show that the Cauchy horizon is compactly generated, and argue that any attempt to build such a spacetime with normal matter might lead to singular behavior where the causality violation would otherwise take place.