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GR and the role of the graviton

by La Guinee
Tags: graviton, role
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Mentz114
#19
Oct29-08, 02:12 AM
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P: 4,087
I'm not so sure now but I do know that for gmn to be a covariant tensor, then under transformation from [itex]x^\mu[/itex] to [itex]x^\bar{\mu}[/itex]
[tex]g_{\bar{m}\bar{n}}=g_{mn}A^n_{\bar{n}}A^m_{\bar{m}}[/tex]
where
[tex]A^n_{\bar{n}}=\frac{\partial x^n}{\partial x^\bar{n}}[/tex]

I don't think [itex]\eta_{mn}+h_{mn}[/itex] satisfies this rule.

I could be wrong, maybe someone can clarify ?
jnorman
#20
Oct29-08, 10:26 AM
P: 308
in my view, quantum gravity (ie, gravitational force as a result of the interaction of graviton particles with other particles) is a non-starter. there is no conceivable mechanism by which particle interaction could result in the perfectly smooth "bending" of light as it passes a massive star.
Fredrik
#21
Oct29-08, 11:59 AM
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Quote Quote by Mentz114 View Post
I'm not so sure now but I do know that for gmn to be a covariant tensor, then under transformation from [itex]x^\mu[/itex] to [itex]x^\bar{\mu}[/itex]
[tex]g_{\bar{m}\bar{n}}=g_{mn}A^n_{\bar{n}}A^m_{\bar{m}}[/tex]
where
[tex]A^n_{\bar{n}}=\frac{\partial x^n}{\partial x^\bar{n}}[/tex]

I don't think [itex]\eta_{mn}+h_{mn}[/itex] satisfies this rule.

I could be wrong, maybe someone can clarify ?
I just assumed that the separation of g into two pieces is done like this: You start with a quantity g, which is assumed to be a tensor. Then you just express it as [itex]g=\eta+g-\eta[/itex] where [itex]\eta[/itex] is defined as the tensor that has components [itex]\eta_{\mu\nu}[/itex] in some coordinate system. That makes sure that both [itex]\eta[/itex] and [itex]h[/itex] are tensors.

It's a bit strange that we have to mention a coordinate system. There will be issues to deal with, like "In what coordinate systems are the components of [itex]\eta[/itex] equal to [itex]\eta_{\mu\nu}[/itex]?". I don't know anything about how those issues were dealt with. It's been about 10 years since that time when I took a quick look at an old article where they did these things. I never tried to really understand it.
Naty1
#22
Oct30-08, 05:41 PM
P: 5,632
Fredrik:
when I try to google for it, this thread comes up in the search results even though It's only been a few hours since I posted the words that matched the search.
You are being watched!!!!

jnorman :
there is no conceivable mechanism by which particle interaction could result in the perfectly smooth "bending" of light as it passes a massive star.
Harsh assessment..you just killed all of string theory....


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