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 Yearling
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Apr
3
comment Does Alcubierre drive allow time travel?
Cool, thanks. ,
Apr
3
comment Does Alcubierre drive allow time travel?
Right. So if you were to shine a light in the direction of travel exactly at the time of departure the light would still arrive before you, correct?
Apr
3
accepted Does Alcubierre drive allow time travel?
Apr
3
comment Does Alcubierre drive allow time travel?
Interesting, I thought that being within GR would somehow prevent you from time traveling as you don't locally exceed the speed of light.
Apr
3
answered Physical meaning of $Tr(\rho ^2)$
Apr
3
asked Does Alcubierre drive allow time travel?
Oct
11
comment Why are some galaxies flat?
Why doesn't this happen to dark matter? Doesn't it still interact gravitationally?
Sep
1
comment Speed distribution of objects in the universe
What do you mean by objects? Are we taking macroscopic bodies, or does this include molecules/atoms?
Aug
20
awarded  Yearling
Oct
25
suggested rejected edit on Percent error calculations dilemma
Oct
23
comment Second Qubit Not Flipped in Hadamard Gate
What you have here is the matrix applied to the first qubit only. This is shorthand for writing $H\otimes 1$. This tensor product yields a 4x4 matrix.
Aug
20
awarded  Yearling
May
17
comment Why does light travel in straight paths?
What kind of an answer are you looking for? General relativity basically almost postulates this. Quantum or classical domain (or both)?
May
4
awarded  Nice Answer
Aug
20
awarded  Yearling
Aug
13
comment Can entanglement be explained as a consequence of conservation laws?
This only becomes weird when the source produces superpositions. If + stands for spinning one way and - is for spinning in the other direction, then $|+-\rangle$ is a perfectly valid state that obeys conservation laws and is not entangled. So is $|-+\rangle$. Ir
Aug
10
answered Why does nonlinearity in quantum mechanics lead to superluminal signaling?
Aug
10
comment Why does nonlinearity in quantum mechanics lead to superluminal signaling?
@drake I don't disagree that observing causality is nice for a theory. But if I understand the OP's question, it is whether nonlinearity implies the existence superluminal communication, ie. whether it is true that (nonlinearity $\implies$ signalling). To answer that you need to either give an example of nonlinearity that does not lead to signalling, or prove that it always does. You've given an example of signalling that implies nonlinearity.
Aug
10
comment Why does nonlinearity in quantum mechanics lead to superluminal signaling?
@BruceConnor Yes, there is an assumption in my comment that I wrote in the brackets. I was being intentionally lenient on that point.
Aug
10
comment Why does nonlinearity in quantum mechanics lead to superluminal signaling?
@drake The problem is that the mere fact that nonlinearity might allow cloning (and therefore signalling) does not mean it necessarily implies cloning and signalling. What if I give you only a single nonlinear operator (because for instance I only know how to build this particular device)? Will this still enable signalling? Are there some properties the operator needs to satisfy in order to enable signalling or will any nonlinear operator do? If you could clarify this in your answer I would be satisfied.