All Questions
11
questions
2
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36
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How does loop quantum gravity handle spacetimes which aren't globally hyperbolic, like the Kerr metric?
Loop quantum gravity assumes spacetime is globally hyperbolic. However, the interior of a Kerr black hole isn't globally hyperbolic, containing closed timelike curves. So, how are Kerr black holes ...
- 31
2
votes
1
answer
89
views
Confusion about timelike spatial coordinates
I'm pretty new to general relativity, and I'm self-studying it using Sean M. Carroll's text on the subject. In Section 2.7, he introduces the notion of closed timelike curves. He gives the example of ...
- 160
0
votes
1
answer
54
views
In Relativity theory, is chronological relation an order relation?
Let $(M,g)$ be a (Lorentz) spacetime, i.e a connected smooth manifold $M$ with a metric tensor field $g$ and a time orientation called future direction which is defined by a smooth timelike vector ...
- 143
2
votes
1
answer
185
views
No inconsistencies due to closed timelike curves in General Relativity
Is there anything wrong with the following argument ruling out inconsistencies with closed timelike curves?
Math
A solution in the context of General Relativity is a pseudo-Riemannian manifold $(M, g)$...
- 917
1
vote
1
answer
44
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A question on the causal hierarchy/ladder and the existence of CTC
What does the existence of CTC imply for the Causal Structure of the spacetime?
Can a strongly causal spacetime have any CTC[without fluctuating the metric]?
Is there any such example?
Can someone ...
- 1,268
1
vote
0
answers
73
views
Should time be a loop or a line?
It's interesting to see that torus was so popular in physics, that it worked so well. There was famous Gauss–Bonnet theorem which stated basically
$$\oint_S K dS= 2\pi \chi(S)$$
where K was the ...
- 3,256
1
vote
1
answer
101
views
Does general relativity predict that it's possible to watch a process playing backwards?
My question is
Let's say you have an object moving through space locally at less than the speed of light. Is it possible to watch that object playing backwards like a record spinning the wrong ...
- 1,668
10
votes
2
answers
759
views
Simplest mathematical model of a causal loop
Is there a simple mathematical model for causal loops? The physics seems pretty involved, but I'm wondering if I can understand just the math of the final answer (similar to how one can understand ...
- 2,193
4
votes
1
answer
577
views
What is the latest science on closed timelike curves? [closed]
In Scientific American (Sept 2014), Lee Billings writes:
Lloyd, though, readily admits the speculative nature of CTCs. “I have no idea which model is really right. Probably both of them are wrong,” ...
- 383
2
votes
1
answer
192
views
Numerical relativity in causally pathological spacetimes
To perform numerical relativity simulations one almost universally adopts the so called "3+1" approach: spacetime is divided up into spacelike slices, each representing a "moment in time". After some ...
- 4,251
5
votes
2
answers
1k
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Does negative energy density (i.e. weak energy condition violation) create closed timelike curves?
I remember reading something about Stephen Hawking denying the fact you can't make CTC's (Closed Timelike Curves) without weak energy condition violation. If this is true, where do the light cones ...
- 527