Graviton

[Waldo]

What is it that the supposed graviton is supposed to do to cause gravity? Does it coinside with relativity ie: does the actual graviton particle repel space-time? Any help would be awesome..

[RyanJ]

A gravition is basically another way to think of a gravitational field, its a concept. Its hard to picture how it woud function if it were a particle in this case so its probably best to think of it as a field. I suppose you can think of it in the sameway as you do how photons can be a form of light and how the light ways can be an example of waves.

 

 

All I know is that gravitions have a 2 spin and are always attractive, sorry if I am of little help

 

Cheers,

 

Ryan Jones

[Perturbation]

It would operate in a similar manner to its wave counter part: gravitational radiation predicted by general relativity.

 

Gravitational waves operate by causing the space between two points to change by altering the geometry (metric) of some region of space-time as they propogate through it. These perturbations in the geometry satisfy the following inhomgenous wave equation in linearised field theory

 

[math]\left(\frac{1}{c^2}\frac{\partial^2}{\partial t^2}-\nabla^2\right)h_{\alpha\beta}=16\pi \frac{G}{c^4}T_{\alpha\beta}[/math]

 

Describing the propogation of linear perturbations of a background Minkowski space-time with phase velocity c, i.e. gravitational waves propogate at c, in the Lorentz(/harmonic/de Donder) gauge. The above equation does, however, only come about if we deal with a weak field and work in a specific gauge, though because the gauge transformations we apply have no physical relevance we're free to choose the gauge ourself.

 

The graviton is the quantisation of this field, as the photon is of the electromagnetic. It's a tensor gauge boson, and thus has spin 2, and the potential it generates is always attractive for a positive mass.

 

The current problem with gravitation on Planck scales comes from this quantisation: can we formulate a gauge invariant renormalisable field theory for gravity? Naive attempts in the 50's set about formulating gravity in a similar manner to the field theories around at the time, these effective field theories were however unrenormalisable (unable to remove divergences from loop-momentum integrals in ultraviolet/infrared limit) or suffered from some other physically undeseriable effect. It is often the case that for one to be able to formulate a quantum field theory of anything we have to have the geometry of the space-time presupposed; however in general relativity the geometry is a dynamic quantity, varying with position and time depending upon the local distribution of matter and its own behaviour.

 

(Loop) Quantum gravity proceeds by constructing a gauge invariant field theory from the Diffeomorphic group (the group of isomorphic, differentiable maps between hyperplanes of the space-time) of the space-time. I've not studied it a great deal though, likewise with M-theory.

[5614]

Simply put: the graviton would do exactly what gravity currently does.

[Waldo]

Yes i understand that gravity would be the same, but my question is does the graviton agree with general relativity or is is a different subject so to speak?

[RyanJ]

Yes i understand that gravity would be the same, but my question is does the graviton agree with general relativity or is is a different subject so to speak?

 

As far as I know it does agree

 

String theory uses the gravition as the particle version of gravity just as it does the photon for light and seeing as it is hoped to be the T.O.E it must act the same I guess

 

Cheers,

 

Ryan Jones

[5614]

Relativity talks about a gravitational field or wave. But the quantisation of the wave (ie. having gravitons) does not effect it at all. Basically, as RyanJ said, they agree.

[Waldo]

good to know. Tahnx alot

[Teotihuacan]

It produces about the straightest line we know of, a kind of inborn compass for all life on this planet. Gravity.

 

Actually, it's a similli of a Venturii effect. With graviton particles whizzing by at narrowly sub light speeds. Masses are attracted to each other. In that same instant, gravitons are expanding the space between the clumps of those same masses.

 

nb. We already use this technology with muons to detect unknown burial chambers etc. within solid masses.