Time travel is the concept of moving between different points in time, often instigated by non-trivially topology of space-time, such as a wormhole. DO NOT USE THIS TAG for questions on changes of coordinate systems, changes of time coordinate, or topologically trivial 'twin paradox' settings.

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Navigating a Time Machine

Notes: The background for this question is working out details of a sci-fi story. Answers to the effect of "time travel isn't possible" or "FTL isn't possible" are therefore not helpful. I'm looking ...
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Is the “Doctor Who” spacetime affected by Hawking's chronology protection mechanism?

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 ...
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Are closed timelike curves generic feature of ANEC-violating stress-energy tensor?

Kip Thorne has shown that in order to create closed timelike curves (CTCs), one needs stress-energy tensor $T^{\mu\nu}$ that violates averaged null energy condition (ANEC). Will $T^{\mu\nu}$ with ...
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Huggins Displacement Theory and Retrocausality

I was looking at the Wikipedia entries on Time Travel and the Grandfather paradox and noticed a paragraph on the so-called Huggins Displacement Theory. I haven't been able to find the source although ...
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Wormholes and the illusion of time?

I was watching a video on Youtube by Brian Greene, "the illusion of time."http://www.youtube.com/watch?v=j-u1aaltiq4 In that video, he introduces to me the idea of a "brane," or a slice of the ...