Questions tagged [closed-timelike-curve]
84 questions
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Do any quantum gravity theories deal with closed timelike curves?
As far as I'm aware, there are no quantum gravity theories that deal directly with closed timelike curves. Some of them (like canonical quantum gravity, causal dynamical triangulation and loop quantum gravity) forbid them outright, others merely…
Slereah
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Homotopy proof of the lack of foliation of the Gödel metric
A common proof of the lack of foliation of the Gödel universe, apparently mostly copy pasted from Hawking and Ellis, goes thusly :
A closed timelike curve must cross a spacelike hypersurface without boundary an odd number of times
A continuous…
Slereah
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10
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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 the evolution of a differential equation of a…
Steven Sagona
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Meaning of closed timelike curves
There are spacetimes that admit closed timelike curves (for example a cylinder, Gödel's Universe, the Kerr-Solution).
But what does it physically mean to move along a closed timelike curve? If i move along a timelike curve, proper time passes. Thus…
Mac Menders
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Are time loops real?
I'm new to physics and I was wondering if time loops (like those seen in the movies Groundhog Day or Edge of Tomorrow) possible?
Oisin Spain
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Closed timelike curves in the Kerr metric
I just read in Landau-Lifshitz that the Kerr metric admits closed timelike curves in the region $r \in (0, r_{hor})$ where $r_{hor}$ is the event-horizon ( I am talking about the case $|M|>|a|$ (subextremal case) here ). Now, unfortunately they…
Johnny
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Kerr spacetime and Carter time machine
In the Boyer-Lindquist-Block III (inside the inner event horizon) exists the so-called Carter time machine. There we can show that for any two points $p,q$ there exists a future-pointing timelike or past-pointing timelike curve.
I'm not sure if I…
Alpha001
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What would a closed timelike curve look like?
What exactly are closed timelike curves. In a metric in which they would exist, what would they look like. What would it be like travelling through them? It obviously wouldn't look like a door. Would it be a region of space that if you wonder into,…
Christopher King
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Closed time loops and causality in general relativity
I always read that GR does not seem to prevent closed time loops. This does not sound too crazy if you could somehow create a traversable wormhole (and move one of the ends fast and long to make the two ends out of sync in your original reference…
user338734
5
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1 answer
Why does a null entropy variation along a closed timelike curve imply a reversible process?
Carlo Rovelli in one of his articles from 2019 (reference: https://arxiv.org/abs/1912.04702) argues that time travel into the past are thermodynamically impossible:
For instance, if we want to travel to the past and arrive to the past keeping our…
MattG88
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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 point to in the $t$ direction?
On the end of the…
user122083
- 537
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Warp drive causality issue, and a possible error in a paper?
Take a look at this paper on "Warp Drives and Causality:" https://doi.org/10.1103/PhysRevD.53.7365
The author attempts to argue that the Alcubierre Drive spacetime could exhibit Closed Timelike Curves, if one is to consider a "Lorentz Transformation…
Joeseph123
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Role of the observer in Gödel's universe
I am here to clarify myself about the role of the observer in Gödel's solution (1949) of Einstein's field equations.
The Universe we are dealing with is anisotropic, since the axis of rotation defines a directional preference, while still…
4
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Wormholes and Closed Time-like Curves
I've been doing a presentation on Wormholes for my Science class, and I've been wondering about the difference of Closed Time-Like Curves and Wormholes, as most articles I read can't truly explain the difference, even most search engines i've tried…
WormholeWanderer
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What is the latest science on closed timelike curves?
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,” he says. Of course, he adds, the other possibility…
Chris Degnen
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