Questions tagged [closed-timelike-curve]

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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 ...
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Impossibility of closed timelike curves

Hawking's Chronology Protection Conjecture says that the laws of nature must always conspire to prevent a CTC from forming. Why can't we conclude that this is proven? An inconsistent CTC is s ...
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Could Gott's Cosmic String Time Machine hypothetically be used as a poor man's Alcubierre drive?

I have read much speculation about Gott's theoretical use of cosmic strings for time travel, but if the colliding cosmic strings accelerated the spacecraft faster than light, as Gott theorizes, could ...
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Where is the CTC region of a Kerr Black Hole?

CTCs are found in the region where $r < 0$ . That should be just inside the ring singularity, since in Boyer Lindquist coordinate system $r = 0$ means ring singularity. Does that mean this image ...
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ADM formalism, closed timelike curves and chronological protection conjecture

Is it correct that based on the premise of foliation by Cauchy surfaces the ADM fomalism restricts the set of solutions for general relativity to causal manifolds and therefore excludes closed ...
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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 ...
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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 ...
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General Covariance & CTCs

Consider Minkowski space defined in coordinates $(t,x,y,z)$. Let us equip the manifold with a time orientation $$T = \frac{\partial}{\partial t}$$ such that $g(T,T)<0$, in $(-+++)$ signature, this ...
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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 ...
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Does faster than light lead to closed timelike curves?

If some signal can be sent to a spacelike interval then is it possible in some reference frame to have a close timelike curve? Novikov claims so in this paper. The argument lies below eq$7$ but ...
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Do wormholes really allow us to travel back in time?

Theories surrounding wormhole based time travel are annoying me tonight... So the way time works is relative, right? The closer you are to the frame of reference, the faster time moves. So, if we use ...
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CTC, determinism and valuedness of Riemann tensor

What I understood is that By the math, the Riemann tensor is obtained by parallel-transporting a vector along a closed curve in the considered space, then apply Stoke's theorem. Now if physics is ...
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In what sense does the "speed limit" $c$ prevent violations of causality? Could they be prevented some other way? [closed]

I have seen it said that if we want to avoid violations of causality (I can see why we would want to avoid that!), we need the information-transfer "speed limit" of c. I presume(?) this ...
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1 answer
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Classical Field Theory with Compact Time

How does one find solutions to a classical field theory (say, $\phi^4$ theory) when the time dimension is periodic (so in $\mathbb{R}^n \times T^1$ or other compact topology), especially if the ...
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If the universe is closed, does that also mean time is closed?

Speaking just about space, we say that the universe is either open (topologically $E^3$) or closed (topologically $S^3$). But since a metric connection defines curvature on spacetime and not just ...
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What Ron Mallett doing for time machine here? [duplicate]

Here Ron Mallett pouring liquid chemical on array of lasers for progress of time machine. I didn't understand it. Source What exactly Ron Mallett doing for time machine here?
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Closed Timelike Curves and relatively stationary wormholes

Apologies in advance if this question is off topic, I wasn't sure if this was the most appropriate SE forum or not. Wormholes are one of the most often cited examples of a possibility for faster than ...
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Let $M$ denote a connected time-oriented Lorentzian manifold. If $M$ is compact then $M$ must have a closed-curve

Problem Let $M$ denote a connected time-oriented Lorentzian manifold. If $M$ is compact then $M$ must have a closed-curve. I don't know how to use this information that M is compact to obtain a ...
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Is there any experimental evidence of CTC?

One consequence of general relativity is a solution called the closed time like curve or CTC...which could allow you to view a place at an earlier point in time or possibly even travel back in time. ...
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1 answer
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Do superluminal worldlines constitute closed time-like curves under the right conditions?

A closed time-like curve is defined as a word-line that returns to its starting point, in the $x$, $y$, $z$, $t$ coordinates. So, for a chronology respecting observer, an object traversing a closed ...
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Can you go back and forth through time when inside a black hole?

Inside the event horizon of a Schwarzschild black hole the radial coordinate becomes timelike and the time coordinate becomes spacelike (they change signatures). I read that timelike coordinates are ...
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Pair creation and annihilation and Wheeler's one electron universe

I stumbled upon Wheeler's idea that there could be only one electron. If I understood correctly, basically the idea is that one electron moves forward and backward in time such that it appears as if ...
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Misner space - closed timelike curves

Could someone give me a good resource to read about closed timelike curves in Misner space? Somewhere where they are actually derived and some comments are made for the simple 2D Misner space?
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Is there any well-known holographic duality that allows wormholes and CTCs to exist?

Is there any well-known holographic duality (like AdS/CFT or holographic principle in string theory/black holes) that contains wormholes and Closed Timelike Curves? I was discussing this with a ...
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Would CTCs in wormholes change physical laws?

A wormhole is a speculative structure linking disparate points in spacetime, and is based on a special solution of the Einstein field equations solved using a Jacobian matrix and determinant. (https:...
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Would non-hyperbolic space times have different laws?

Would a non-hyperbolic model of our universe have fundamentally different laws than our universe? For example, in Gödel's metric, its laws would be described by general relativity. But if the Gödel ...
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Time Travel, CTC and Causal Loop

What is the difference between a closed timelike curve and a causal loop? If someone is travelling in a closed timelike curve, are they also in a causal loop?
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Brouwer fixed point theorem

How does the Brouwer fixed point theorem (which provides a solution to the photo camera paradox of a causal loop) generalise to show that objects in closed time-like curves do not violate the second ...
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2 votes
1 answer
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Correlators for space-like photon bouncing

Consider the diagram below of two detectors-emitters exchanging photons: Thin lines are null-paths between detectors. Detectors are also synchronized in such a way that measurements outside the blue ...
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Is a time loop possible? [duplicate]

Let's say that hypothetically we could travel faster than light. Would a ship travelling at lightspeed or faster than light travel create a time loop where it makes the same trip over and over again ...
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Closed Trajectories in wormhole

This might seem trivial but if I want to go about finding closed trajectories in a wormhole with a metric: $$ds^2=-dt^2+dr^2+(b^2+r^2)(d\theta^2+sin^2\theta d\phi^2)$$ how should I approach that? Is ...
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10 votes
2 answers
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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 ...
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3 answers
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Closed spacelike vs Closed timeline curves (or rather loops)

Reading John Rennie's answer, it made it very clear as to why it is justified to talk of time as a coordinate. So, for now we put time and space on the same footing i.e. consider them dynamical ...
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4 votes
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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 ...
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1 vote
0 answers
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Causally benign spacetimes and the Minkowski torus

A notion encountered in field theory on non-globally hyperbolic manifolds is the notion of a spacetime being causally benign with respect to some field $\phi$, which is defined thusly : A ...
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Physical reality of inner event horizon and inner ergosurface in a rotating black hole in D. Wiltshire et al. "The Kerr spacetime"

In chapter 1/The Kerr spacetime-a brief introduction by Matt Visser of D. Wiltshire, M. Visser, S.M. Scott "The Kerr spacetime - Rotating black holes in general relativity" the author presents a ...
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2 votes
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Does our universe admit of a global time function?

My understanding of a global time function is this: a function whose value always increases as a body moves into its local future. My confusion is this: I gather that the Gödel Universe is bizarre ...
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Accelerating thin shell wormholes and closed timelike curves

The classical example of the conversion of a wormhole into a time machine is to consider two wormholes, one stationary and another one accelerating for some period before going back to its original ...
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What is a closed timelike curve? [closed]

I was wondering if anyone could explain to me what a closed timelike curve is? From Wikipedia: "In mathematical physics, a closed timelike curve (CTC) is a world line in a Lorentzian manifold, of ...
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1 answer
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What would a closed timelike curve be like? [closed]

I have a few questions about CTC: What would CTC look like from the outside? Would every loop be the same? What would happen if the cause of CTC disappear? (e.g. Tipler cylinder stopped spinning)
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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?
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4 votes
1 answer
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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 ...
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1 vote
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Experimental test for a universal scale closed timelike curve?

So recently, in chat, I was interested in about what if our universe contains only one CTC (thus making it unlike the Gödel metric, van Stockum dust where there can be more than one CTCs found) and ...
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Geodesics and CTC

What is the exact explanation for which CTC (closed timelike curves) are not geodesics? I have already looked up in many papers but none provides the exact reason.
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Time travel backwards, would anything be observable? [closed]

I'm by no means a physicist theoretical or otherwise, so please do excuse any things that I may be ignorant of (likely a very long list). If by whatever mechanism a traveller were able to travel back ...
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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,” ...
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5 votes
2 answers
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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 $|M|>|a|$ (...
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Detection of closed timelike curves (CTC)

I have a question. Are there any methods for detecting CTC? Is there a possibility of designing modern physics experiment in order to confirm / refute the possibility of CTC at any given time in a ...
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28 votes
3 answers
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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 ...
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4 votes
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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 every two points $p,q$ there exists a future-pointing timelike ...
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