Not on but of. by Olaf Dreyer

Dear Olaf,

I do not agree with you that matter is simply is excitation of the background. The matter is particles which compose substance of bodies. The field is originated by particles of matter at the low levels of matter, and the field holds the form of particles. The excitation is a consequence of interaction of ensembles of particles. It may be a wave or a quantum such as photon. Such picture is a conclusion of the Infinite Hierarchical Nesting of Matter (my essay). You can compare your results with mine. For the first the cosmological constant was explained in the paper: Fedosin S.G. The Principle of Least Action in Covariant Theory of Gravitation. Hadronic Journal, February 2012, Vol. 35, No. 1, P. 35 - 70. The cosmological constant is proportional to the density of substance of system at infinity where the gravitational field disappears. For the second you can include gravity in quantum mechanics taking the Lorentz-invariant theory of gravitation (LITG) and changing the gravitational constant by Strong gravitational constant. And do not forget Gravitational torsion field since the spin torsion field counteracts to strong gravitation in atomic nucleus. Due to the effect of Gravitational induction nucleons in nucleus are rotated quickly changing their spin.

And also the model of gravitation and Newton law are deduced: Fedosin S.G. Model of Gravitational Interaction in the Concept of Gravitons. Journal of Vectorial Relativity, March 2009, Vol. 4, No. 1, P.1-24.

Sergey Fedosin Essay

A pretty good read ... Is there any difference between particles being an excitation of the background - as you describe - and an aether medium?

Interpreting gravity as a form of Casmir force is clever.

You might be interested in the work of Milo Wolff. He is an advocate of a wave media for both forces and particles.

Regards,

Gary Simpson

Houston, Tx

Dear Gary:

Thank you for your comments.

There is an interesting difference between what I am proposing and the old style aether theories. In the old theories the aether was a physical medium that was everywhere and it carried the electromagnetic field. Matter on the other hand was not an excitation of the aether. Matter was to aether what boats are to water. This is the crucial difference to what I am saying. In my thinking both fields and matter are both excitations.

Yep ... you would like Dr Wolff's work. He solved the spherical wave equation ~25 years ago and concluded that it constitutes an extended spatial structure. He interprets it as the electron and positron.

Regards,

Gary Simpson

Houston, Tx

Dear Olaf

I've read your essay with great interest. It is really intriguing, and presents relly fresh new original ideas, very promising. I'm very interested in Modified Newton Dynamics (MOND), since I think that from a new approach to quantum gravity we may get some modification of the gravity law, which is beyond the sensitivity of available experiments. I'd love to discuss more with you about.

For the moment I've just a stupid simple question about your essay (which shows that I've not really understood some technical part).

Eq. (10) seems to have a dependence of G with the gravitational mass of the object (since a is the radius). I looked everywhere for the meaning of m, but also in your previous paper "Internal relativity" I found the same. Am I understanding right? Shouldn't be G a universal constant?

My best to you

and compliments again

Mauro

Dear Mauro:

Thank you so much for the kind words!

The dependence of G on m is a true issue. Let me explain how I think about that:

A similar issue arises with the speed of light c. In generic solid state models the speed of an excitation will depend on the particle species. There are exceptions though. In Volovik's models that rely on a Fermi point all excitations have the same speed that is given by the shape of the Fermi surface near the Fermi point.

I think that the situation is similar with G. Generically G depends on the species but there are models where G will be the same for all species. This does not require that all particles have the same mass because it is the quotient of m and the radius r that is important. What is needed is thus that the mass and the radius scale in the same way. Intriguingly this is exactly what happens for a Schwarzschild black hole (r = 2m).

One should also note that in an emergent theory one does not have the freedom to add emergent particles at will. One can change the underlying theory at will but because the process of emergence is non-trivial it is not immediately clear what the emergent theory will be like. It is hence not that trivial to create a theory that has particle species with arbitrary mass to radius quotients.

Thanks again for the interest.

Olaf,

"The spin-wave above is an excitation of the background not an excitation on the background.

Gravity appears because the ground state θ depends on the matter. The picture of gravity that we have given in the last section is valid only for zero temperature."

Do most physicists subscribe to the "of" position, for example Lawrence Krauss in his new book? My essay deals with gravity and the possibility of cancelling it. I'm not sure how your "of" position would affect it. Any thoughts?

Jim

Dear Olaf,

This is a very interesting set of ideas you are proposing. I particularly appreciate your identification of the "cosmological constant problem" as an artifact of background dependence. I have a few questions:

1. What are the implications for the microstructure of "spacetime?" If one assumes that matter-energy is a way of talking about "spacetime" excitations, then it seems "spacetime" might be very nonmanifold-like at small scales.

2. As you know, many of the properties of "elementary particles" in quantum field theory are determined by the representation theory of the Poincare group of symmetries of Minkowski spacetime. Even in GR, this is a priori problematic because the spacetime will interact with the matter energy it "contains," thereby complicating the use of spacetime properties to determine particle properties. When you go a step further and view particles as part of spacetime rather than just interacting with it, this seems to deepen the problem further. What type of constraints would one use to replace the Poincare symmetries in this general context?

3. The only "respectable" approach to quantum gravity I know of that claims to solve the "cosmological constant problem" is Sorkin's causal sets. What do you think about this "solution?"

Thanks for the interesting and informative submission! Take care,

Ben Dribus

Hi Olaf,

In the late '50s and early '60s, Wheeler also pursued the idea that matter is an excitation of the background space-time in his "geometrodynamics" program. Are their points of contact between his research program and yours?

Steve

PS: Check out my essay, if you like: http://fqxi.org/community/forum/topic/1529.

Dear Jim:

Thanks for having a look at my essay!

I think it depends who you ask. There are basically two schools here. The first school consists of elementary particle physicists and they subscribe completely to the "on" position. Usual quantum field theory is a theory of fields on spacetime. The other school consists of solid state physicists. For them the "of" picture is very natural because that is how they encounter particles; as quasi-particles. I am not sure which school is larger. There are a lot of elementary particle physicists but there might just be more solid state physicists.

If one takes the "of" point of view then there is still the question of how gravity arises. It could either be a an emergent excitation (the graviton) or it is a non-perturbative effect. It is this second possibility that I am suggesting.

I am not sure about canceling gravity. I think in my model gravity would always be attractive. I am going to have to look at your essay.

Cheers

Olaf

Dear Ben:

Thanks for the interest in my essay! Here are my replies to your questions:

1. The micro-structure of spacetime would definitely not be manifold-like. The smoothness of the spacetime would only arise in the large scale/low energy limit. A smooth spacetime would be to the fundamental micro-description as the surface of water to water molecules.

2. The argument here would be that the construction that starts with the symmetries and then discovers the particles through representation theory has it exactly backwards. The symmetries arise from the way the excitations behave. An example here is the spin model by Wen in which QED arises in a theory of spins. The underlying theory consists of spins on a lattice but the emergent theory is (approximately) Lorentz invariant (because it is QED).

3. In causal set theory the cosmological constant can be explained by looking at the fluctuations of the number N of points in a volume. These fluctuations go like the square root of the volume. If one assumes that the cosmological constant and the volume are a conjugate pair this implies that the cosmological constant can not be exactly zero because of these fluctuations. Putting in the numbers one gets a result that is of the proper order of magnitude.

This is a very interesting observation but I am not sure what it means. My main confusion stems from the foundations of the causal sets program itself. Because the program is somewhat abstract (how do you go from the points to the spacetime?) it is very unclear to me what the cosmological constant is in this context. A cosmological constant should expand spacetime but if the points carry all the information about the metric how does the cosmological constant do that? Nevertheless it is an interesting argument to keep in mind.

There is one more person that argues he has a solution to the cosmological constant problem: Volovik. His arguments are very interesting and they fit very well with the program I presented here.

Thanks again for the interest! Now on to your paper ...

Cheers

Olaf

Steve!

Thanks for having a look at my essay.

I think Wheeler tried to see if the bound states of pure gravity (he called them geons) could play the role of elementary particles. This would be a very economic way of organizing the world. All that is needed is the gravitational field. My program is very similar in spirit but I do not start with the gravitational field. Instead I allow for more general kind of backgrounds. This makes the emergence of particles much easier (I do not have to construct a geon) but the emergence of gravity itself is now much harder.

Hope to see you around sometime soon!

Now on to your essay...

Cheers

Olaf

See my discussion with George Ellis

http://fqxi.org/community/forum/topic/1337#addPost

Just waiting George answer...

Hey Olaf,

Hope things are well!

I really enjoyed reading your essay, especially the simple model you use to get the MOND-like behaviour. Indeed, this model is a lot simpler than some of the other entropic gravity approaches. Very cute indeed! Flavio and I give a simple toy model, based on shape space, in our essay that gives a holographic behaviour. I wonder if there could be any connections between your particle models and shape space?

There is one thing that confuses me though. Can't the cosmological constant problem be stated without any reference to matter? If you just look at free gravity and use dimensional arguments then the cosmological constant should have dimensions of mass squared. But then the *dimensionless* cosmological constant has to be massively fine tuned to agree with the measured value. So the fine tuning problem is already in free gravity. Right?

Cheers,

Sean.

Hi Olaf,

I know about Milgrom's result but I have not seriously looked at the consequences for SD. I had one crazy idea recently (if you'll allow me to indulge ;-). The conformal group in 3d is SO(4,1), which is the isometry group for de Sitter. Thus, I think a natural action for SD is the one of Stelle and West that uses an SO(4,1) connection because it can be decomposed into a conformal geometry in 3d.

Now, how do you couple fermions to this action? You can't use normal spinors because the space is locally de Sitter NOT locally Minkowski. Thus, you shouldn't use spin 1/2 reps of the Poincarre group but rather spin 1/2 reps of the de Sitter group (which, is isomorphic to the conformal group). But, because the cosmological constant is small, these "dS spinors" should be effectively the same as standard spinors, at least for particle physics experiments. You would only notice a difference in the dynamics at cosmological scales related to the cosmological constant (because this is what distinguishes the dS group from Poincare). But the MOND scale is the cosmological scale! So maybe you would expect MOND like behavior from the SO(4,1) spinors?? And maybe the relation to scale invariance is because of the isomorphism with the conformal group??

I don't know... but I'd like to look into this at some point! Did that make sense??

I take you're point about the cosmological constant problem. You're right that the story might change once we have a good theory of quantum gravity. Now I understand your point. Thanks!

Cheers,

Sean.