# Faster than the speed of light

1. Nov 21, 2004

### Arash

Howdy All
Yesterday i read an article about a particle with the velocity faster than the speed of light but as the text was not in english i couldn't understand the particles name to do research over it.
It was like " Taxion " or "Toxion" !
Does anyone have any information about this particle or any particle which its speed is faster than the speed of light?
Thanks you very very much
Arash

2. Nov 21, 2004

### imabug

the theoretical (speculated) particle you are looking for is the tachyon. AFAIK there is currently no credible proof of its existence.

3. Nov 21, 2004

### Tom McCurdy

Indeed the tachyon was used in such things as primitive versions of super string theory, however with the incorperation of the idea of super symmetry the tachyon was no longer needed.

here is a good site to get some more info on it
http://en.wikipedia.org/wiki/Tachyon

4. Nov 22, 2004

### NeutronStar

Interesting Tid-Bit

Someone please correct me if I'm wrong, but if I recall correctly the tachyon would not only be faster than the speed of light, but it could also never be made to travel slower than the speed of light.

Assuming, of course, that it even exists in the first place.

5. Nov 23, 2004

### Gecko

yup, its speed is only above the speed of light, it takes an infinite amount of energy to make it go slower than light.

6. Nov 25, 2004

7. Dec 8, 2004

### saltrock

Nice article....like it as its very informative

8. Dec 8, 2004

### 600burger

Hey all,

Does anyone know the orign of the tachyon "theory"? I heard/learned it was derived from noticing symmetry with so many other things, and its an anti-matter of something...

-Burg

9. Dec 8, 2004

Staff Emeritus
The original tachyon (back in the sixties) was created by imagining a particle with pure imaginary mass - that is, its mass squared was to be a negative number. If you plug that into the normal dilation formulas you get a real number answer for v > c. The dilation physics turned inside out, the faste a tachyon went above c the easier it was, the slower it went, approaching c from above the more energy that took, and so on. Perfectly sound mathematics but "unphysical" implications.

Then a tachyon, with mass squared less than zero, was discovered in the spectrum of the bosonic string...

10. Dec 9, 2004

### Ivan Seeking

Staff Emeritus

[Wakes up from long sleep]

When, where... I have been away from physics for awhile but when did I miss this?

11. Dec 9, 2004

Staff Emeritus

Ivan, the tachyon as the lowest energy vibration of the closed bosonic string goes back as far as the graviton, twenty years, I guess. It's in all the textbooks. The "rest of the story" is that when they incorporated supersymmetry to create the superstring theories, they suppressed the tachyon and thought they were home free. But not so, tachyons, rolling tachyons, and just about every kind of tachyon you could imagine are features of the string landscape you hear so much about, and one of the hot topics in current research.

12. Dec 9, 2004

### Ivan Seeking

Staff Emeritus
Okay, so they are again expected but this is still completely theoretical, right?

You mathematicians; when you said discoveredmath I thought that you meant discoveredphysics.

Last edited: Dec 9, 2004
13. Dec 9, 2004

Staff Emeritus

Surely you didn't expect a physical discovery out of string theory?

14. Dec 9, 2004

### Ivan Seeking

Staff Emeritus
I don't know what I was thinking!!! :surprised

15. Dec 10, 2004

### ZapperZ

Staff Emeritus
I think "imagine" is the operative word here! :)

<runs and hides>

Zz.

16. Dec 10, 2004

### marlon

It's like this :

without making any exotic and "metaphysical" jumps to string-theory i will provide you with the QFT-picture...

In "our experimentally backed-up QFT" the tachyon-particle is a quantum of a field whose squared mass is negative. The tachyon exists because of symmetry-reasons. More specifically, the existence of such a particle implies the instability of the spacetime vacuum. The reason for this instability is the fact that there are more then one minimal potential-values.

Now, a little excitation of the vaccuum-state will result in spontaneous breakdown of symmetry. Imagine that you would give small impulse to the field, this will lead the field to roll down with exponentially increasing amplitudes: it will induce tachyon condensation: The tachyon will become a particle of positive mass.

Once "nature" has chosen ONE specific vaccuum-state of minimal potential energy, the tachyons will no longer exhibit negative mass. The reason for this is that symmetry-properties of the system (the Lagrangian) have changed.

regards
marlon