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 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

    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

    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 Sean:

      Thanks for the interest!

      I am going to have a look at your model. Very curious to see how you are getting the holographic behavior. In connection with that there is a question that I always wanted to ask you: Do you know this paper by Milgrom?

      The Mond Limit from Spacetime Scale Invariance

      The Astrophysical Journal vol. 698 (2) pp. 1630

      Is there a connection between your work on gravity and this? I am asking because both of you stress scale invariance. Have you looked at that?

      Your statement about the cosmological constant is correct. In an effective quantum field theory view of gravity your argument leads to a problem without the introduction of matter. A problem I have with that view is that you have to rely on a theory (pert. quantum gravity) that we know has problems. In the argument involving matter the only thing you need to know about gravity is that it reacts to the presence of energy. You don't even need to know anything about quantum gravity.

      It is also true of course that the cosmological constant problem without matter does not make the cosmological constant problem with matter go away. If you think of matter as sitting on spacetime the problem is there.

      Now on to your essay ...

      Cheers

      Olaf

      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.

      4 days later

      Dear Olaf,

      It has a while since I heard anything new about you. While I admit I liked your older work more still good to see you back. I hope you check out what I have done maybe it will give you an idea. Sorry for doing copy and paste from my other posts but it should be enough to give you an idea.

      In my theory everything is emergent all from a mathematical structure that describes random numbers and imperative relations between them. Interpreting the random numbers as line lengths, the relations between these lines generate all of the laws of physics. You get a beautiful unified picture of space (its points are the crossing of the lines-dynamic-), time(change of state-does not actually exist-), mass, charge, and energy.The theory is called "Quantum Statistical Automata".

      It is a kind of an automata conjectured by Wolfram and Conway, but mine derived from a more fundamental idea of why reality had to come about. Of course Dr Tegmark is also a believer in the mathematical universe. I did not know any of these great people back then, but I came to believe that reality is nothing but a mathematical structure and went directly to the simplest system to implement such program. I hit on the right system in no time due to a combination of a flash of brilliance (which we all experience), my engineering/problem solving background and extraordinary luck.

      From the following results it can be seen that the system shows how ordinary physics results arise plus some results that standard physics can only dream of. But the most important conclusion is that the system points to the REAL final theory. All is needed is some smart people to take it seriously, or wait for me to finish it up in due time. Of course the former will be much quicker than the later.

      Fundamental Theory of Reality,"Reality is nothing but a mathematical structure, literally".

      1. How I arrived at the idea.

      2. Basic results that shows how QM arises, written in BASIC program.

      3. Description of two particles interacting and explaining the program in C++.

      4. Showing the results for Bohr atom hydrogen 1s simulation.

      5. 1/r law and the running phase

      6. The amazing formulas deduced from the system.

      7. How spin arises from 2D simulation.

      8. The appearance of the mass of the electron through simulation.

      WORLD'S First, I am not Kidding.( it won't hurt to chuckle though)

      9. How gravity arises.(basic simulations not shown yet)

      There are many other results not shown.Attachment #1: 5_newqsa.pdf

      Dr. Dreyer,

      Hi. As with many of the more mathematical essays here, I can't say I understood all of your paper because I'm a biochemist and not a physicist or mathematician, but I can say that based on my own thinking, what you're saying makes a lot of sense, and I will give you a high rating with my vote. I would further add that just about everything, including matter and energy and everything else, is an excitation of, or emergent from, a background. My reasoning would be something like:

      1. In thinking about the question "Why is there something rather than nothing?", I've come to the conclusion that there is a fundamental existent state, and it doesn't matter if this state is called matter, energy, something, nothing, quantum fluctuation, mathematical construct, causal set, etc.

      2. Because our universe has more than one existent state in it, this initial state must have had some way of replicating itself to create more states, which would then be able to create yet more states, thus leading to a big bang-like expansion of space and volume that we call the universe. Thus, our universe, our existence, is made of an expanding sea, or set, of existent states.

      3. Because we have movement in our universe, there must have been some mechanism for allowing these existent states to change and transfer this change to adjacent states, in the form of energy. Since we're talking about the physical universe, the existent states would have to be three-dimensional states, and the most basic way I can think of for a 3D existent state to change would be a change, or deformation, in its shape which it can somehow transfer to adjacent states.

      4. Because our universe is made of these existent states, everything we see around us, must be excitations within, or of, these states.

      To postulate that in addition to the fundamental existent state there is something (e.g., matter) totally different that's "sitting on", as you mentioned, this sea of states, doesn't make much sense. If we really want a unified theory of everything, it makes sense to me that there would be excitations within a sea, or set, of replicas of the fundamental existent state. You can't get much more unified than that, I don't think.

      If you're interested, my model for how the above might happen based on proposed solutions to the questions of "Why do things exist?" and "Why is there something rather than nothing?" was the subject of my last FQXi essay from the last contest and is at my website at:

      https://sites.google.com/site/ralphthewebsite/filecabinet/why-things-exist-something-nothing

      You could also try the main site at https://sites.google.com/site/ralphthewebsite

      and click on the third link.

      Anyways, from this amateur's viewpoint, good essay, and good luck!

      Roger Granet

        If you do not understand why your rating dropped down. As I found ratings in the contest are calculated in the next way. Suppose your rating is [math]R_1 [/math] and [math]N_1 [/math] was the quantity of people which gave you ratings. Then you have [math]S_1=R_1 N_1 [/math] of points. After it anyone give you [math]dS [/math] of points so you have [math]S_2=S_1+ dS [/math] of points and [math]N_2=N_1+1 [/math] is the common quantity of the people which gave you ratings. At the same time you will have [math]S_2=R_2 N_2 [/math] of points. From here, if you want to be R2 > R1 there must be: [math]S_2/ N_2>S_1/ N_1 [/math] or [math] (S_1+ dS) / (N_1+1) >S_1/ N_1 [/math] or [math] dS >S_1/ N_1 =R_1[/math] In other words if you want to increase rating of anyone you must give him more points [math]dS [/math] then the participant`s rating [math]R_1 [/math] was at the moment you rated him. From here it is seen that in the contest are special rules for ratings. And from here there are misunderstanding of some participants what is happened with their ratings. Moreover since community ratings are hided some participants do not sure how increase ratings of others and gives them maximum 10 points. But in the case the scale from 1 to 10 of points do not work, and some essays are overestimated and some essays are drop down. In my opinion it is a bad problem with this Contest rating process. I hope the FQXI community will change the rating process.

        Sergey Fedosin

        Hi Olaf,

        Glad you're interested. There might be a clue to how to do this in Hans Westman and Tom Zlosnik's new preprint. But they seem to look at what I'm suggesting but they find no change from Dirac-GR. Apparently there are some terms that cancel. In any case, I would like to understand this better. Maybe there is a way to get something like the MOND behaviour.

        Anyway, take care and good luck in the competition!

        Sean.

        Sergey G Fedosin is bombing entrants' boards with the same "why your rating has dropped" message. They are all dated Oct. 4... same message.

        WTH? I've seen one fine essay drop 89 (eighty-nine) positions, in "Community Rating" in the past 24 hours, and "Sergey's note" came BEFORE it plummeted. Hmm.

        The vote/scaling of this contest is quite nebulous.

        "Hackers Rule!", I suppose!

        Well??? What else is one to think? The General Public is... Watching...