3 papers
hep-th2005
Unitarity in the Presence of Closed Timelike Curves
Lorenzo Cornalba, Miguel S. Costa
We conjecture that, in certain cases, quantum dynamics is consistent in the presence of closed timelike curves. We consider time dependent orbifolds of three dimensional Minkowski…
hep-th2003
Time-dependent Orbifolds and String Cosmology
Lorenzo Cornalba, Miguel S. Costa
In these lectures, we review the physics of time-dependent orbifolds of string theory, with particular attention to orbifolds of three-dimensional Minkowski space. We discuss the p…
hep-th2003
On the Classical Stability of Orientifold Cosmologies
L. Cornalba, M. S. Costa
We analyze the classical stability of string cosmologies driven by the dynamics of orientifold planes. These models are related to time-dependent orbifolds, and resolve the orbifol…