gravitation among individual particles

**area_man** · Nov7-09, 03:27 PM

I understand in general the types of situations where GR, Newtonian Gravity, and the Standard Model are usually used.

What puzzles me is this: since the LHC is being used to look for the Higgs Boson, that suggests that the SM can explain gravity if the Higgs Boson is found.

If that is indeed the case, will the SM and Higgs Boson explain all that GR does and predict all that GR predicts, thus replacing GR, or will GR and the SM still be separate entities that are not connected in any obvious way?

**Cleonis** · Nov7-09, 04:33 PM

Originally Posted by area_man

I understand in general the types of situations where GR, Newtonian Gravity, and the Standard Model are usually used.

What puzzles me is this: since the LHC is being used to look for the Higgs Boson, that suggests that the SM can explain gravity if the Higgs Boson is found.

If that is indeed the case, will the SM and Higgs Boson explain all that GR does and predict all that GR predicts, thus replacing GR, or will GR and the SM still be separate entities that are not connected in any obvious way?

Well, the Standard Model is a quantum theory that is compliant with the postulates of special relativity.
The Higgs mechanism, designed to be part of the Standard Model, complies with the postulates of Special Relativity.

Gravitation, however, is outside the scope of the Standard Model, just as gravitation is outside the scope of special relativity.

(By the way, a quantum physics can also be formulated for newtonian space and time. To be self-consistent it's not necessary for quantum physics to comply with special relativity. Early on in the development of quantum physics observation confirmed the expectation; only the SR compliant version agrees with observation.)

As I understand it: in itself confirmation of the Higgs mechanism will not establish connection between the Standard Model and General Relativity. Still, it is hoped that the LHC results will provide leads to a successor to the Standard model.

Cleonis

**D H** · Nov7-09, 04:44 PM

Originally Posted by area_man

What puzzles me is this: since the LHC is being used to look for the Higgs Boson, that suggests that the SM can explain gravity if the Higgs Boson is found.

The Higgs mechanism explains why leptons and quarks have the mass they are observed to have. The Higgs mechanism does not explain gravity.

**area_man** · Nov7-09, 05:12 PM

Great information from all parties; thanks!

So if I understand correctly, GR explains gravitational force as arising from a distortion of space-time by mass. The standard model will have an explanation for why mass exists if the Higgs Boson is discovered. But even now, physicists are comfortable with gravity affecting quarks and leptons due to mass-induced space-time distortions exactly as predicted by GR. Even at that scale (leptons and quarks), physicists believe GR behaves the same as it does for large masses like planets, stars, and galaxies.

Have I got it?

thanks again,

a_m

**Cleonis** · Nov8-09, 10:06 AM

Originally Posted by area_man

So if I understand correctly, GR explains gravitational force as arising from a distortion of space-time by mass. The standard model will have an explanation for why mass exists if the Higgs Boson is discovered. But even now, physicists are comfortable with gravity affecting quarks and leptons due to mass-induced space-time distortions exactly as predicted by GR. Even at that scale (leptons and quarks), physicists believe GR behaves the same as it does for large masses like planets, stars, and galaxies.

Have I got it?

It's difficult to say whether you 'got it'. For some reason you keep suggesting there are scale issues, in places where there aren't any.

Let me begin with recapitulating how Electromagnetic interaction is conceived. It's thought of as being mediated by a field, and that EM-field is an occupant of spacetime. The EM field resides in spacetime, just as particles reside in spacetime.

In the case of gravitational interaction the mediator is not thought of as a field that resides in space, the very spacetime itself is thought of as being distorted.
That idea should make anyone uncomfortable. Can we still think of particles as being subject to gravitation? Arguably everything in spacetime (curved or uncurved spacetime) is just floating along, in inertial motion. It's very counter-intuitive.
Anyway, there is no room for any scale distinction: celestial bodies or subatomic particles, everything is in spacetime, floating along in spacetime. In terms of GR space is assumed to be smooth, GR gives no hint to suppose otherwise, so in terms of GR floating in (curved) spacetime is the same at any scale.

Cleonis

**area_man** · Nov8-09, 12:18 PM

Thanks again Cleonis.

If there is no scale distinction then are we left with a situation where the gravitational force is understood to result, fundamentally, from mass-induced space-time distortion, whereas other forces like the electromagnetic force result from a completely different phenomenon (force-carrier particles)?

For example, do physicists believe that coulomb forces are the result of a space-time curvature caused by charge, or is it only gravity that is caused by space-time curvature? If that's the case, it's interesting that such basic forces are seen as arising from such dissimilar causes.

**Cleonis** · Nov8-09, 12:50 PM

Originally Posted by area_man

[...] is it only gravity that is caused by space-time curvature? If that's the case, it's interesting that such basic forces are seen as arising from such dissimilar causes.

Yes, Electromagnetic interaction and Gravitational interaction are described with very different kinds of theories. In their current forms quantum physics of the Standard Model and General Relativity cannot be unified into a coherent structure.

We have to assume that Nature itself is a coherent structure.
(If Nature itself would be unstructured, how come theories can be formulated at all?)

The general expectation is that somewhere down the line a successor to the current theories will be developed/found, achieving unification, but so far none of the avenues that have been explored have been fruitful.

Cleonis

**area_man** · Nov8-09, 01:14 PM

Thank you VERY much, Cleonis. I truly appreciate the time you and others have spent helping me to understand this better. It is very generous of you and the other posters.