tachyons

[ydoaPs]

has anyone come up with a theory on how tachyons would be created if they were to exist?

 

could tachyons be part of the dark matter? if they exist, their imaginary mass energy may prived predictable effects in the gravity around galaxies. i don't know any of the GR equations, so i wouldn't be able to see what happens when you put an imaginary term in for mass\energy.

[rajama]

From our perspective, a tachyon's rest mass is an imaginary quantity... but to a tachyon it isn't: in it's own reference frame it would be real, wouldn't it? Just like it's speed relative to other tachyons would always be less than C..?

 

I'm not overly familiar with GR either - I have a number of dusty text books - but you seem to be asking whether the mass of a particle following a space-like trajectory contributes to (observable) spacetime curvature..?

 

I'm going to go with (tosses coin) yes

 

... er, is that thunder in the distance??

[rajama]

Did you get anywhere with your query, maybe via another route..?

 

I assume (now) it was about particle production – not that I noticed at the time…

 

I’m returning to this thread because I had a related thought a few weeks back while looking at the superluminal thread in SFN Relativity.

 

Maybe someone could feedback on this?

 

It relates to the association of an imaginary rest mass with a tachyon… or a particle occupying a superluminal inertial frame (IF) relative to another frame.

 

I looked over several derivations of SR and it seems to me the idea of an imaginary rest mass is incorrect, and yet it seems common coin among those who discuss the subject…

 

The imaginary mass relies on (1-v*2/c*2)^1/2 being an imaginary quantity, which it is for v > c.

 

This equation in turn is derived by some kind of ‘range finding’ experiment - bounce a photon off a moving object, time its flight, etc.

 

This kind of experiment cannot relate positions in two frames with relative speed greater than c because it involves the path of a single photon / light beam measured in both inertial frames… which can’t be done.

 

It’s a Pythagoras exercise gone wrong, not the basis of extending SR.

 

I think we need another transform…???

 

So, after banging my head against a wall for a while, I put one together... before posting it, can I ask is anyone interested in taking a look?

 

I assume I'm re-inventing the wheel here, so any expert input would be much appreciated...

[rajama]

Mmmm... no response.

 

Well, I'll drop a few diagrams and related equations in the 'Speculations' area to avoid annoying anyone – see if anyone has any comments

 

Thanks anyway…

 

(I assume yourdadonapogos has moved on)

[Severian]

(I assume yourdadonapogos[/b'] has moved on)

We can always hope.

 

A tachyon would be rather bad, since its presence would indicate an unstable vacuum.

[ajb]

For a good review of tachyons in string theory see http://arxiv.org/abs/hep-th/0410103

 

For a field theory view see http://arxiv.org/abs/hep-th/0204143

 

I worn you both are advanced and not for beginers.

 

Severian is right, in quantum field theory tachyons are due to our poor choice of vacuum when doing pertubation theory. However, in string theory which is usually formulated via first quantisation things are not so clear. The first review paper I suggested deals with this.

[rajama]

there are people out there!

 

Originally Posted by Severian

A tachyon would be rather bad, since its presence would indicate an unstable vacuum.

 

Originally Posted by ajb

Severian is right, in quantum field theory tachyons are due to our poor choice of vacuum when doing pertubation theory. However, in string theory which is usually formulated via first quantisation things are not so clear. The first review paper I suggested deals with this.

 

Many thanks to both for the feedback and references (169 pages?).

 

I'm really only familiar with undergraduate physics (what little I remember) and have been playing around with SR and the 'classical' tachyon hypothesis, so you're right in guessing any string theory papers will blow me away...

 

I assume from your comments tachyons are considered a pathology in a theory or indicative of unrealistic boundry conditions...

 

I think I'll still post what I have as a 'speculation' as the feedback may be helpful.

 

Also, I've almost finished writing a first draft - even if its rubbish at least the effort is keeping my brain alive.

[ajb]

 

I assume from your comments tachyons are considered a pathology in a theory or indicative of unrealistic boundry conditions...

 

 

They indicate that you have done your pertubation expansion around an unstable vacuum. This false vacuum will decay to a stable true vacuum. In doing so we get particles that now have positive mass squared. It is not really the boundary conditions on the fields that are the problem, but our poor choice in selecting a vacuum to expand about.

 

In string theory it is hoped that a similar thing may happen to remove tachyons. This is under the name "tachyon condensation".

[ydoaPs]

We can always hope.

I love you too, Severian!

[rajama]

They indicate that you have done your pertubation expansion around an unstable vacuum. This false vacuum will decay to a stable true vacuum. In doing so we get particles that now have positive mass squared. It is not really the boundary conditions on the fields that are the problem, but our poor choice in selecting a vacuum to expand about.

 

In string theory it is hoped that a similar thing may happen to remove tachyons. This is under the name "tachyon condensation".

 

I read the field theory paper in your second reference, and it soon became clear it was actually written in some form of english - way beyond my background, I'm afraid, but thanks anyway...

 

It did prompt me to tour wikipedia pages on false vacuum and related issues...

 

Also, I just published that speculation - it's called 'Superluminal Inertial Frames in Special Relativity?'.

 

Have fun.

[ajb]

 

Also, I just published that speculation - it's called 'Superluminal Inertial Frames in Special Relativity?'.

 

 

Where did you publish it?

[rajama]

Where did you publish it?

 

ah, sorry, no - not 'publish' in that sense - it's just a few notes sitting in the speculations forum which is of course way way down at the bottom of the main page, where (currently) 30 people have viewed it and no one has commented...