17 questions linked to/from Do tachyons move faster than light?
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### Tomorrowland movie and tachyons? [duplicate]

Would be possible if tachyonic existed to send info to the past or see the future? since the tachyons according to special relativity could travel to the past? i have searched in wikipedia and the ...
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### Can one classify partial differential equations according to the causality properties of their solutions (and if yes, then how)?

Recently, I bumped into this interesting comment by Valter Moretti which made me wonder about the following, more general question (to which I suspect the answer is affirmative): Can we easily tell, ...
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### What if a faster-than-light particle is found?

What will be the consequence (severe ones) on laws of physics if a particle that travels faster than light is discovered? I am looking for a more general answer so that a high school student would be ...
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### Why don't people use Hamilton's equations for a relativistic free charged particle?

A charged relativistic free particle has the Hamiltonian in general: $$\mathcal{H} = \sqrt{{\bf p}^2c^2+m^2c^4}.$$ I read somewhere that says, it is possible to go further and say that the EoM are ...
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### Would a tachyon be able to escape a black hole?

Or at least escape from a portion of the hole inside the photon horizon?
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### How do we know tachyons don't exist?

As I mentioned yesterday, Hollywood screenwriter working on a TV pilot about physics trying to get the details right. What empirical evidence is there that tachyons do not exist? I understand that ...
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### If Tachyons exists, can they escape event horizon?

I was just wondering that, Tachyons travel faster than the speed of light. So in theory, if Tachyons exists can they escape event horizon?
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### Does negative mass reverse the arrow of time?

General relativity predicts that normal mass (positive mass) results in the curvature of spacetime which in return leads to gravitation. Since space and time are bonded together, any change on the ...
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### Could dark matter/dark energy turn out to be tachyonic?

Today, I was watching the Inexplicable Universe with Neil deGrasse Tyson. He spoke about Dark Matter, Dark Energy, and then he spoke about Tachyons. Naively, I thought what if the reason we can't ...
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### Can strings go faster than light?

I have been wondering if strings in string theory can go faster than light, as it is one dimensional when it does not vibrate? So do the same limits apply to it, I googled it but could not find a ...
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### Is there any theory in physics that might support the existence of tachyons?

According to Einstein, we all know that light is the fastest thing and it's impossible to beat it's speed. But isn't there a way to go around this? I read somewhere that tachyons gain speed per the ...
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### Does the commutator of two quantum fields $\phi(x)$ and $\phi(y)$ vanish for $(x-y)^2<0$ and $m^2<0$?

The commutator of two free scalar fields at two spacetime points $x$ and $y$ given by $$[\phi(x),\phi(y)]=\int\frac{d^3p}{(2\pi)^32E_{\textbf{p}}}[e^{-ip\cdot (x-y)}-e^{ip\cdot (x-y)}]$$ is Lorentz-...
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### Can the momentum of a system be spacelike?

For a particle, we always have $Eu=p$ where $u$ is the speed of the particle and correspondingly the momentum is always timelike. For a system of particles, if the potential energy is not considered ...