Recently, there has been a paper1 (and an accompanying layman-ized white paper2) on "Traversable Achronal Retrograde Domains In Spacetime", TARDIS for short. It proposes a spacetime geometry that contains closed timelike curves.
Now, Hawking once proposed3 a mechanism that apparently causes all closed timelike curves to more or less destroy themselves. Basically, quantum fluctuations cycle through the curve and build upon themselves (in a sense, they overlay with their "past selves"), leading to a divergent expectation value for the energy-momentum tensor.
The media (which has dubbed it the "Doctor Who spacetime") seems to have caught on to this paper as the next time machine. Usually, the term "closed timelike curve" is associated with time machines because of the causality violations a CTC can cause.
Is this really possible? Or does Hawking's mechanism protect this system from a causality violation, destroying the CTCs in it?
1. arXiv:1310.7985 [gr-qc]; "Traversable Achronal Retrograde Domains In Spacetime", Benjamin K. Tippett, David Tsang
2. arXiv:1310.7983 [physics.pop-ph]