Essay Abstract

In physics we encounter particles in one of two ways. Either as fundamental constituents of the theory or as emergent excitations. These two ways differ by how the particle relates to the background. It either sits \emph{on} the background, or it is an excitation \emph{of} the background. We argue that by choosing the former to construct our fundamental theories we have made a costly mistake. Instead we should think of particles as excitations of a background. We show that this point of view sheds new light on the cosmological constant problem and even leads to observable consequences by giving a natural explanation for the appearance of MOND-like behavior. In this context it also becomes clear why there are numerical coincidences between the MOND acceleration parameter $a_0$, the cosmological constant $\Lambda$ and the Hubble parameter $H_0$.

Author Bio

Olaf Dreyer is a theoretical physicist working at the university in Rome. He received a PhD in Quantum Gravity at the Pennsylvania State University and has worked at the Perimeter Institute, Imperial College, and the MIT, where he was supported by a fqxi grant.

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  • Post #2

Dear Olaf

Are you agree with my abstract?

http://fqxi.org/community/forum/topic/1413

    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

      Dear Yuri:

      Thanks for the interest in my article. In your article you mention these four assumptions that need changing:

      1. 4D spacetime.

      2. Gravity as a fundamental force.

      3. 3 fundamental dimensional constants(G,c,h).

      At this level of discussion I would agree with all of them. In my view the 4D spacetime is only an emergent object and not fundamental, gravity is emergent, and because of that the gravitational constant G can not be of fundamental importance. In fact I provide a formula for G in my essay. The devil is of course in the details.

      I particular like the last sentence of your essay:

      "I would really wish to those who are working in the field of fundamental physics problem to not remain unemployed."

      8 days later

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      • Post #6

      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

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        • Post #7

        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.

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        • Post #9

        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

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          • Post #11

          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

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              • Post #14

              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.

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                • Post #15

                Dear Sergey:

                Thank you for your interest in my essay. I was trying to understand what your theory says about the cosmological constant but I could not quite understand it. It seemed to me that the cosmological constant is not really constraint in your framework.

                Cheers

                Olaf

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                • Post #16

                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

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                • Post #17

                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

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                • Post #18

                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

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                • Post #19

                See my discussion with George Ellis

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

                  Dear Yuri:

                  I just had a look at the discussion. Unfortunately it seems somewhat inconclusive. You do not seem to want to supply the details that G. Ellis is asking for. Are you working on a longer reply?

                  Cheers

                  Olaf

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                  • Post #21

                  Just waiting George answer...