Karsten Bormann

Self-consistency of the quantum billiard problem in wormhole spacetimes

A wormhole can be made to function as a time machine. In the context of the quantum billiard problem in the presence of a wormhole we examine whether this is compatible with the self-consistency of physics. We derive a self-consistency condition in which the classical limit corresponds to known results for the (classical) billiard problem in a wormhole space-time and that suggests that some fine-tuning of initial conditions might be necessary.

Time Machines and the Breakdown of Unitarity

We present a generic way of thinking about timemachines from the view of a faraway observer. In thismodel the universe consists of three (or more) regions:One containing the entrance of the time machine, another the exit, and the remaining one(s) therest of the universe. In the latter we know ordinaryquantum mechanics to be valid and thus are able to writedown a Hamiltonian describing this generic time machine. We prove that the time evolutionoperator is nonsymmetric. Various interpretations ofthis irreversibility are given.

Problems in time-machine construction due to wormhole evolution

We take the dynamics of wormholes into account when discussing the construction of time machines. Criteria for time travel to be possible are derived.