Dear Dr. Crowther,

I really enjoyed your essay. I found it to be a very insightful examination of current physical theory and the aspects that make them fundamental or not.

I wonder about some of the requirements, such as being non-perturbative, since some things simply cannot be computed mathematically in a direct fashion. Could such requirements imply that there might never be a fundamental theory?

My group has been working on an attempt at a foundational theory called Influence Theory,

Knuth, K.H., *Bahreyni, N. 2014. A potential foundation for emergent space-time, Journal of Mathematical Physics, 55, 112501. doi:10.1063/1.4899081, arXiv:1209.0881 [math-ph]

Knuth, K.H. 2014. Information-based physics: an observer-centric foundation. Contemporary Physics, 55(1), 12-32. doi:10.1080/00107514.2013.853426. arXiv:1310.1667 [quant-ph]

and you now have me thinking about to what degree what we have achieved so far is fundamental.

Thank you for your excellent essay!

Kevin Knuth

Dear Karen,

Thank you for writing this paper which while it aims at assembling the criteria that are used by working physicists in their construction of fundamental theories is at the same time provocative and gives one a lot to think about.

I am not convinced that this list is best presented as a set of criteria on what high energy physicists look for in a fundamental theory as opposed to a final theory. You are clear at several points in the paper that you think we should not make a distinction between 'fundamental' and 'final'. But I would disagree. It is clear we are far away from a final theory and yet there is an importance to recognizing at least part of current physics as fundamental. Our best physical theories have a special explanatory status not shared by other attempts at characterizing the world that underwrites their status as fundamental. I try to articulate the importance of such characterization in my own essay submission.

I also wanted to ask about "weirdness". Many would argue that any realist interpretation of quantum theories is going to commit us to some weirdness, in forcing us to move beyond assumptions that were previously thought of as obvious. Shouldn't some weirdness be allowed even in a final theory of physics?

Best,

Alyssa

    There is both physical evolution as also the biological evolution. Both have followed the logic built in to the Nature! Your essay has touched on both these aspects but have refrained from discussing these two aspects seperately and in conjunction. Evolution is basically a natural event and can not be understood through scientific knowledge which itself is in the process of evolution. Philosophy reflects human thinking but it has also developed a kind of methodology! These are our constraints in ' free will ' understanding! Thus, the questions remain open and 'freedom' of thought and action remains open, without restriction due to history of science that we may have happened to evolve thus far.

    Dear Karen,

    You are the victim of a targeted attack of massive downvoting. Me too. Also I noticed Andrew Beckwith was attacked too, maybe others, but so far I only noticed you two. This may be the result of a desperate last minute attempt to climb the ladder, but it is dishonest and a violation of the rules of the contest, in which case we are advised to write to the organizers. Which I did, and Andrew did it too. I would encourage anyone who noticed such phenomena to report them.

    Good luck!

    Cristi

      Dear Christi,

      Thanks for this. Yes, I was very surprised to notice such a drop today without any accompanying comments! So I will write to the organisers, as you suggest.

      Good luck for you, too!

      Karen

      Dear Karen,

      A belated answer to your bottom line question; 'What is the interpretation of the question that could be answered by "Yes"?'

      My answer is that when the question is read as a literal statement of fact requiring confirmation, either the word 'What' is fundamental or it is not. Hence the alternative 'one word' answer is either 'Yes' or 'No'.

      Since you didn't respond on my essay page, I am wondering whether you rated my essay. There is something 'going on' on the closing day for the acceptance of essays that suggests that some authors are drastically low-ranking the essays of others in the expectation that they may benefit as a result. If you didn't rank my essay, could you kindly do so, hopefully to return my rank to its former 'high tide' position of 6.8?

      Again, you carry my best wishes as you move forward into the sunshine, the final phase of the contest, and far beyond.

      Gary.

      Karen, Christi,

      I can ask even if it's awkward for either of you: Does this downvoting appear to be gender related? You both have very good essays, so it's strange to see both of you hit by this.

      My observation to any FQXi admins reading this: Please at least consider whether there has been some bias here. All I can say is that the high quality of these two essays has not changed, so a sudden downswing in the last couple of days to me just seems wrong.

      Sincerely,

      Terry Bollinger (63 year old male codger, since my first name is ambiguous... :)

      13 days later

      Dear Karen,

      I found your essay very clear! Unlike some others, it came exactly as announced in the abstract. :) I think your text is very accessible and relevant for, e.g., Master students of physics. (I would definitely have enjoyed reading such a survey at that point, to add some global perspective to more detailed courses of QFT, etc.)

      Three more detailed comments on section 4:

      - On p. 6 it appears that you assume the "problem of missing physics" (as Wilson calls it; i.e., the existence of gaps between theories) is only temporary. (In my own essay I have embraced the patchwork view of physics, as I think it is here to stay.) I am not sure whether rejecting patchwork is necessary for embracing the goal of physics (which you discuss at the bottom of p. 7): searching for a unique, unified, ... theory may well be the goal of physics, but I don't think it is inconsistent to admit at the same time that it is an unattainable one.

      - "No weirdness" is a tricky requirement - as you may well be aware of -, since what we find weird or not strongly depends on our training and background knowledge.

      - I particularly appreciate how you managed to escape Kantian worries by keeping us focused about what physics is (and isn't) about. So, I fully agree with your comment at the bottom of p. 7: indeed, physics isn't in the business of finding out what are things-in-themselves.

      Best wishes,

      Sylvia - Seek Fundamentality, and Distrust It.

        Dear Alyssa,

        Thank you for your comments. Sorry for my delayed response.

        My idea in this essay was to provide the apparently necessary conditions on a fundamental theory of physics - not just a 'currently fundamental' physical theory. GR and QFT (or, really, some particular QFTs, like QCD) are both currently fundamental, and yet physicists are still searching for a deeper theory, for reasons that I present in the essay. And this is what led to me eventually realising that the distinction between fundamental and final needed to be dropped, due to the arguments regarding unification and uniqueness.

        Regarding weirdness: the idea was motivated by the fact that so many physicists remain unconvinced that the framework can be complete, or correct, due to the measurement problem. Many people (physicists and philosophers alike) believe that a more fundamental theory (perhaps QG) must provide a solution to the measurement problem, and thus absolve this 'weirdness'. So, the lesson I took is that some degree of weirdness may be acceptable, but there may be a point where the theory is weird enough that it won't be accepted by mainstream physics as a fundamental theory, and people will seek to go deeper. (That said, I am not fully convinced by this condition, because the measurement problem could plausibly be "external" to theory... So I will think about this more).

        Best,

        Karen

        Dear Armin,

        Thanks very much! (And sorry for the delayed response).

        You raise some very good points here, and offer a new perspective for viewing my essay. Yes, as you appreciate, I was taking the particular perspective of current mainstream high-energy physics, and trying to discover and articulate the conditions it apparently puts on a fundamental theory (while leaving open the possibility that these conditions change in the future). But, as you note, these conditions are revealing of the nature of the discipline itself at this point in time, beyond its conception of fundamentality. So, yes, I would certainly like to take up this idea in future work, and to better understand what it is about these conditions that makes them key to current physics -- and what may be modified in future physics.

        Your project sounds like it could be a very difficult one! I'm curious what you mean, so I'll come have a look...

        Best,

        Karen

        Dear Sylvia,

        Thanks very much!

        Yes, you raise some good points here, and I agree. Regarding the "patchwork": it may well be that we continue to work in this way, building up a patchwork, ultimately aiming at a unified, unique theory, but also recognising that in the end we may have a set of theories. Actually, this is similar to comments in the paper on UV completion (with Niels Linnemann) -- that a UV complete theory may be an ultimate goal, and heuristically useful, but we can still use UV incomplete theories, and at the end of the day, that may be all we have (though of course currently in QG, the non-renormalisable theory we have is unsatisfactory since it breaks down at the Planck scale, which is what we want to describe). Really, I think this whole list represents an unattainable goal that nevertheless drives us!

        Regarding "no weirdness" -- yes, it's a tricky one. I certainly wouldn't want to reduce it to what particular individuals, or particular research programs find weird, but some rough sort of disciplinary consensus. When a theory is unsettling enough that many researchers forge ahead for something deeper, and this research is recognised as legitimate by mainstream physics (or, at least, not entirely misguided)... that's the gauge of "weirdness" I mean. But I need to think about this more... Please let me know if you have any more thoughts on it!

        Best,

        Karen

        Write a Reply...