A Does attraction vs repulsion depend on graviton spin?

[Heidi]

Hi Pfs,
I read somewhere that if the graviton had a spin 1, then gravity would be repelling.
Is there a formula showing that the attract-repel depends on the parity of the carrier's spin?
thanks

 

[berkeman]

I read somewhere that if the graviton had a spin 1, then gravity would be repelling.

You have 405 posts here at PF and post "I read somewhere..."? Please post a link...

 

[Heidi]

Sorry,
I did not say where because i am not sure i could trust it:
https://www.quora.com/Quantum-Field...s-particles-of-even-integer-spin-only-attract
I think that this can be read somewhere else. Maybe on Physics forum.

 

[berkeman]

Sorry,
I did not say where because i am not sure i could trust it:
https://www.quora.com/Quantum-Field...s-particles-of-even-integer-spin-only-attract
I think that this can be read somewhere else. Maybe on Physics forum.

Quora would not usually be a valid source. Can you please try to find an original source, preferably in a peer-reviewed journal?

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[Vanadium 50]

if the graviton had a spin 1, then gravity would be repelling.

That statement, in so far as it has meaning at all, is wrong. Everything repels everything else? I am not sure that's even a logical possibility, and in any event that's not the property of a spin-1 field. A statement like "two identical fermions would repel under an Abelian spin-1 mediated interaction" is at least specific enough to be discussed.

However, I don't think it's PF's job to hunt down justification for what random people post on other sites, like Quora or Youtube.

 

[Heidi]

Can we consider that it was a false start?
It begins now like that:

I have in my hand a book written by Antony Zee.
It is Quantum field theory in a nutshell.
Zee writes on page 26 of my edition :
The presence of two delta function sourcs at x1 and x2 has lowered the energy.
In other words the two sources attract each other by the virtue of theit coupling to the scalar
field phi.

The next paragraph is Coulomb and Newton repulsion and attraction.
He writes: we saw that the exchange a spin 0 particle produces an attratice force,
of a spin 1 a repulsive force, of a spin 2 an attractive force.
That was the origin of my question.

Zee consider the 3 cases separately and found these results.
Does it come from just one rule or formula or principle?

 

[Vanadium 50]

At least we have a well-defined question. Unfortunately, I do not know if there is a general "rule". (Or if there is, if most people could understand it) Spin-0 and spin-1's difference comes from the (anti-)commutation properties of γ matrices, Spin-0 doesn't have any, and spin-1 has one. That's where the relative minus sign comes from.

The sorts of spin-2 theories one can write down are very restricted. I am not sure if this argument extends that far or not.

 

[Demystifier]

Hi Pfs,
I read somewhere that if the graviton had a spin 1, then gravity would be repelling.
Is there a formula showing that the attract-repel depends on the parity of the carrier's spin?
thanks

If graviton had spin 1 then it would be like a photon, i.e. it would obey equations of electrodynamics. As you know, in electrodynamics two positive charges repel.

 

[haushofer]

If graviton had spin 1 then it would be like a photon, i.e. it would obey equations of electrodynamics. As you know, in electrodynamics two positive charges repel.

Or maybe a more general vector boson based on some SU(N) gauge group and a non trivial beta function

Feynman's book on gravity contains some stuff about this, but I'll have to check what exactly.

 

[Heidi]

Does this depend on the dimension of space time?
I think of the dimensions which are added in string theory.

 

[Vanadium 50]

Does this depend on the dimension of space time?

Does what exactly depend on the dimension of space time?

 

[Demystifier]

Does this depend on the dimension of space time?
I think of the dimensions which are added in string theory.

No, the action for electrodynamics (in covariant form) looks essentially the same in any number of dimensions.

 

[Heidi]

Another question:
Are there theories with higher spin than the graviton, carrying interactions?

 

[renormalize]

Another question:
Are there theories with higher spin than the graviton, carrying interactions?

Steven Weinberg offers this comment in The Quantum Theory of Fields I, pg. 253:
"The fields of massless particles of spin $j\geq 3$ would have to couple to conserved tensors with three or more spacetime indices, but aside from total derivatives there are none, so high-spin massless particles cannot produce long-range forces.

 

[Heidi]

Antony Zee describes the early universe.
Structures emerged with denser regions where protons and neutrons were close together.
The attractive nuclear force mediated by the spin 0 particle eventually ignites stars.
What are these spin 0 oarticles. (the gluons spin is 1) ?

 

[Demystifier]

The attractive nuclear force mediated by the spin 0 particle eventually ignites stars.

I guess he talks of pions, which in effective models can the thought of as carriers of nuclear force.