Tachyons and Superluminal motion:

[beecee]

HI!!! Great to be back....

This question of mine was inspired by a comment from Mordred in the Gravity thread....

• Quote

  ^{_{"whether superluminal motion would guarantee the ability to escape an event horizon is a question (albeit a purely academic one) that isn’t straightforward to answer."}}  

  Thoughts??

[Strange]

1 hour ago, beecee said:

a comment from Mordred

It was actually Markus:

On 1/29/2020 at 6:51 PM, Markus Hanke said:

Static gravity does not propagate, so no gravitons need to escape an event horizon.
Gravitons would need to be massless spin-2 bosons, and as such move at exactly the speed of light, just like photons and gluons.

As a side note - whether superluminal motion would guarantee the ability to escape an event horizon is a question (albeit a purely academic one) that isn’t straightforward to answer.  

I thought it was an interesting comment too.

I guess the reason is that it is non trivial to work out what the path of a superluminal particle would be (perhaps because the whole theory is built on the assumption that nothing can move faster).

 

[beecee]

11 hours ago, Strange said:

It was actually Markus:

I thought it was an interesting comment too.

I guess the reason is that it is non trivial to work out what the path of a superluminal particle would be (perhaps because the whole theory is built on the assumption that nothing can move faster).

 

Apologies to Marcus.

[MigL]

17 hours ago, Strange said:

the reason is that it is non trivial to work out what the path of a superluminal particle

I do remember reading that a superluminal particle ( tachyonic, derived from the root of -1 in the denominator of SR's Lorentz transforms ) travelling backwards in time, is equivalent to creating one at the destination and travelling forward in time, to the source. This would go some way to preserving causality.
The 'idea' of these imaginary ( from i , root of -1 ) particles has been largely set aside, but the imaginary fields ( 'sourcing' these particles ? ) can often be a useful tool.

[Strange]

20 minutes ago, MigL said:

I do remember reading that a superluminal particle ( tachyonic, derived from the root of -1 in the denominator of SR's Lorentz transforms ) travelling backwards in time, is equivalent to creating one at the destination and travelling forward in time, to the source. This would go some way to preserving causality.
The 'idea' of these imaginary ( from i , root of -1 ) particles has been largely set aside, but the imaginary fields ( 'sourcing' these particles ? ) can often be a useful tool.

Yes, it is straightforward to calculate their (somewhat paradoxical) behaviour using SR. But presumably somewhat more complex in GR.

[Mordred]

What makes the question even more complex is the tachyon wavefunctions must be subliminal. There is a particular rule for this though I would have to dig for it as I can't recall the name atm. If I recall correctly Beaz mentions it in one his tachyon articles.

Edit I was right it's Paley Weiner theorem 

http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html

 

Edited February 17, 2020 by Mordred

[Markus Hanke]

11 hours ago, Mordred said:

What makes the question even more complex is the tachyon wavefunctions must be subliminal. There is a particular rule for this though I would have to dig for it as I can't recall the name atm. If I recall correctly Beaz mentions it in one his tachyon articles.

Edit I was right it's Paley Weiner theorem 

http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html

 

Very interesting. Thanks for posting!
This immediately begs the question of how a full GR treatment of tachyon propagation would look like. Given non-locality, how would one describe their world lines (if that’s even meaningful)? How do they couple to background curvature? How would they behave around event horizons, and regions of geodesic incompleteness? Etc.

Edited February 18, 2020 by Markus Hanke

[Strange]

14 hours ago, Mordred said:

Edit I was right it's Paley Weiner theorem 

http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/tachyons.html

At the end of that it says: "localized tachyon disturbances are subluminal and superluminal disturbances are nonlocal" which made me think of entanglement: like, is there some analogy possible between the model of tachyons and entanglement...

[Mordred]

On 2/17/2020 at 10:21 PM, Markus Hanke said:

Very interesting. Thanks for posting!
This immediately begs the question of how a full GR treatment of tachyon propagation would look like. Given non-locality, how would one describe their world lines (if that’s even meaningful)? How do they couple to background curvature? How would they behave around event horizons, and regions of geodesic incompleteness? Etc.

Lol how indeed, particularly with the particle as a field excitation view such as QFT. 

20 hours ago, Strange said:

At the end of that it says: "localized tachyon disturbances are subluminal and superluminal disturbances are nonlocal" which made me think of entanglement: like, is there some analogy possible between the model of tachyons and entanglement...

This qets tricky when dealing with quantum non locality. There is a lot of misunderstanding on what that term actually means.

https://arxiv.org/abs/1901.07050

There is similarities in the commutation in terms of nonlocal commutations between paly Weiner and the Hilbert commutations mentioned in the article. This is one area the two have similar meaning (lol considering Paley Weiner is essentially applying a Hermitean space. The reasoning would be identical. (commutations vs non commuting variables)

Edited February 19, 2020 by Mordred

[Mordred]

 Quite honestly I'm trying to figure out how wave particle duality works in this instance. The pointlike attributes can be superluminal but the wavelike being subluminal lol.

Glad the title of Beaz article " Is Tacyons real " seems appropriate.

[Strange]

4 hours ago, Mordred said:

 Quite honestly I'm trying to figure out how wave particle duality works in this instance. The pointlike attributes can be superluminal but the wavelike being subluminal lol.

I am visualising it as the wave function being so "spread out" (non local) that it includes any space that the particle could get to at superluminal speed.

[Mordred]

Lol good a visual as any.