Peculiarities of quantum field theory in the presence of a wormhole

In this paper, quantum theory of a real massive scalar field in the background of a traversable wormhole is examined. The wormhole is supposed to connect two different universes; as a particular example the simplest Ellis wormhole is considered. It is shown that the resulting theory possesses a doubling of quantum states parametrized by the same value of asymptotic momentum; two different sets of such degenerate states are localized in different universes. This is a consequence of the topological structure of the wormhole spacetime, which is the same as the topological structure of the Schwarzschild spacetime providing a similar degeneracy of quantum states.