  In this paper time machines are constructed from anti-de Sitter space. One is
constructed by identifying points related via boost transformations in the
covering space of anti-de Sitter space and it is shown that this Misner-like
anti-de Sitter space is just the Lorentzian section of the complex space
constructed by Li, Xu, and Liu in 1993. The others are constructed by gluing an
anti-de Sitter space to a de Sitter space, which could describe an anti-de
Sitter phase bubble living in a de Sitter phase universe. Self-consistent vacua
for a massless conformally coupled scalar field are found for these time
machines, whose renormalized stress-energy tensors are finite and solve the
semi-classical Einstein equations. The extensions to electromagnetic fields and
massless neutrinos are discussed. It is argued that, in order to make the
results consistent with Euclidean quantization, a new renormalization procedure
for quantum fields in Misner-type spaces (Misner space, Misner-like de Sitter
space, and Misner-like anti-de Sitter space) is required. Such a
"self-consistent" renormalization procedure is proposed. With this
renormalization procedure, self-consistent vacua exist for massless conformally
coupling scalar fields, electromagnetic fields, and massless neutrinos in these
Misner-type spaces.
