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Author Topic: Warped space, branes & gravitons  (Read 3440 times)

Offline DoctorBeaver

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Warped space, branes & gravitons
« on: 18/06/2007 17:28:21 »
I've just been overloading my poor little rodent brain reading a book about these beasties. The theory (known as RS1) is that 2 branes border a 4th dimension of space (4D) that is warped. Our visible universe resides on 1 brane (the Weakbrane) along with all the standard model particles. These particles are anchored to the Weakbrane and cannot move in the 4th spatial dimension.

Gravitons, however, originate on the other brane (the Gravitybrane). As they travel across the 4th spatial dimension towards the Weakbrane, their energy reduces exponentially as their distance from the Gravitybrane increases. On the Gravitybrane, a graviton has a mass of 1Mpl but by the time it reaches the Weakbrane this has reduced to 1TeV (10-16 less). This, apparently, explains the enormous difference in energy between the graviton and other force-carrying particles.

However, what the book doesn't explain is how the gravitons know where to go. There they are, happily wombling off across 4D towards the Weakbrane, losing energy exponentially - but how do they know where the mass is that they are supposed to affect?

Does RS1 mean that all mass affects the 4D to the extent that it attracts gravitons? Or does mass reside across the 4D and cause the release of gravitons from the Gravitybrane?

The book also explains the RS2 theory in which the Gravitybrane is the only brane and gravitons are localised adjacent to it (the furthest from the brane they can go is the Planck length). But I have the same problem with RS2 as with RS1.

Does anyone here know enough about these theories to explain how gravitons interact with mass to cause gravity?
« Last Edit: 18/06/2007 17:32:37 by DoctorBeaver »


 

Offline syhprum

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Warped space, branes & gravitons
« Reply #1 on: 18/06/2007 19:24:55 »
All I know about Gravitons is that they are supposed to have a mass of 10^-11 that of a Neutrino but I have been told not to believe in them.
 

Offline DoctorBeaver

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Warped space, branes & gravitons
« Reply #2 on: 18/06/2007 19:31:06 »
In that book they are predicted to have a mass of about 1TeV. This is in the range of energies that will be possible in the LHC at Cerne. So, maybe we will have an answer fairly soon  :)
 

Offline Soul Surfer

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Warped space, branes & gravitons
« Reply #3 on: 20/06/2007 12:56:38 »
Googling keywords has not produced any clear references only abstracts of papers.

My understanding of gravitons is that they are like photons and their energy is Planck's constant times the frequency  ( h.nu ). When you think about the difference between electromagnetic and gravitational interactions the big difference is the frequency or duration of the interaction.

electromagnetic interactions usually take microseconds (radio waves) or much less.  Quantum effects only start to become significant in interactions below one nanosecond (masers)  and electromagnetic photons only become significantly energetic at much higher frequencies  X-rays and Gamma rays.

Now most gravitational interactions take minutes hours or years  this means that the quanta are incredibly low energy and there are vast numbers of them.

Gravitational quanta will only become significant when the interactions are taking similar short periods to electromagnetic ones i.e. at incredibly high energies, densities and temperatures.
 

Offline DoctorBeaver

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Warped space, branes & gravitons
« Reply #4 on: 20/06/2007 13:02:13 »
I don't have the book with me, but when I go & get it I'll dig out a few quotes from it.
 

lyner

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Warped space, branes & gravitons
« Reply #5 on: 27/06/2007 12:24:58 »
Quote
Googling keywords has not produced any clear references only abstracts of papers.
You will just have to go down to the library and order a paper, then.
That was the only way, a few years ago!
I remember, in the war, son . . . . . .
 

Offline DoctorBeaver

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Warped space, branes & gravitons
« Reply #6 on: 27/06/2007 15:03:51 »
Quote
Googling keywords has not produced any clear references only abstracts of papers.
You will just have to go down to the library and order a paper, then.
That was the only way, a few years ago!
I remember, in the war, son . . . . . .

So do I - the Trojan war  :(
 

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Warped space, branes & gravitons
« Reply #6 on: 27/06/2007 15:03:51 »

 

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