Andrew Jaffe has posted his review of The Goldilocks Enigma: Why is the Universe Just Right for Life? by Paul Davies. Which is an entertaining read, and got me to thinking (okay, what follows doesn’t exactly qualify as thinking, BTW) So some physicists want to use anthropic principles as a solution to the problem of explaining the physics of our universe. But why stop at explaining things like the value of the cosmological constant? Why not go for something bigger, like the question quantum foundations people love: “why quantum theory?” So a challenge: derive quantum theory from the anthropic principle. Do that and I might even begin to believe that the anthropic principle actually has some value beyond making me shout out in pain when reading anthropic arguments 🙂

Why not answer the “why quantum theory?” question? Because, as far as I know, we don’t have a continuum (or even a discretuum, which is apparently a nice usage from the string theory people) of alternative solutions.

With fundamental constants, we at least understand what the parameter space is — what values the constant could take other than the one we observe. Real numbers, generally — maybe positive ones. That’s what allows us to make anthropic arguments. We posit an ensemble of universes, described by a distribution over (for instance)

alpha, and then we postselect on it supporting life. Well, that’s the idea… in practice it’s a bit hazy.Anyway, I don’t think anybody’s got a parameter space containing “quantum mechanics” as one point. The string theory discretuum is about as close as anything of which I know — but all the various theories and vaccua assume quantum mechanics, so that’s a somewhat superficial analogy.

So, counterchallenge: invent a plausible parameter space containing quantum theory (and where the other solutions aren’t manifestly illogical).

Paremeter space = all nonlocal hidden variable models.

Also: quant-ph/0508211

another very general parameter space reference:

quant-ph/0611119

Re all nonlocal hidden variable theories:

How about all local non-real theories?

or all local contextual theories?

Are these even well-defined parameter spaces?

So a challenge: derive quantum theory from the anthropic principle.I think that it can be done, but the mistake that drives you to find humor in the idea comes from the fact that you would first have to do what Brandon Carter said needed to be done, which was to complete this “line of thought”.

The AP is an incomplete stability principle, so you have to figure out how humans are relevant or necessary to the stability mechanism. You have a bunch of otherwise unexpected balance points that are relevent to the structure of the universe, but also point uniquely at carbon based life, so why would that be?… in other words. Figure that we’re *necessarily* woven into the structure in a *special* way via the least action principle, and then read-up on determistic quantum mechanics, because we ain’t here by accident if that’s true.

OHHHH… you meant the weak AP.

Sorry can’t help you with nonesense, but I can tell you that a true anthropic constraint on the forces will *necessarily* include a reciprocal connection to the human evolutionary process, which means that you should be looking for a mecahnism that enables the universe to “leap” to higher orders of the same basic structure, which makes absolute symmetry an unrealizable *goal*.

http://www.lns.cornell.edu/spr/2006-02/msg0073320.html

It should be noted that I find ALL ideas humorous, including the ones that seem to actually describe our universe 🙂

Okay, I deserve a slight whipping for (a) posing a challenge, and then (b) not responding to the response. Barrett’s paper looks interesting, but it’s 24 pages long and I’m frankly intimidated just now. My gut feeling is that “nonlocal hidden variable theories” is too ill-defined a set, but I haven’t a leg to stand upon.

So, this is one of those things that I’ll come back to if SFI decides to hire me… or if somebody else makes some really provocative claim. Until then, I’m intrigued, but too lazy to figure it out!

Re: James Graber’s post — is “Basic Logic and Quantum Entanglement” really the paper you meant to link to? A quick skim leaves me baffled as to its especial relevance.

Re: island’s commentary — I’m sympathetic to certain

limitedconnections between human evolution and physics, but none of that is really relevant here. What I believe we’re talking about is the “very very weak” AP, which says roughly, “Universes in which (e.g.) stars can’t form, or where the CMB has a temperature of 10^6 K, can be ruled out.” It’s probably hard enough to find a theory consist with the existence of earth-like planets.Robin,

I wonâ€™t try to defend â€œespecial relevanceâ€ of the reference. The point I was trying to make is that is â€œall nonlocal hidden variable modelsâ€ is a pretty restricted parameter space. To go to the other extreme, why not start with the AP and say set theory and try to â€œderiveâ€ quantum mechanics?

The two things I like about the Zizzi paper (in this context) is thinking about QM as a point in a set of logics, rather than in some generalization of Hilbert space or something similar, and the nice set of generalizations supplied by the cube of logics. Of course, you must assume that you can extend from quantum logic to quantum computing to full quantum mechanics to connect with the original challenge.

P.s. I am very curious why you have a gut feeling that the space of all nonlocal hidden variable theories is ill-defined? I agree it needs defining, but that doesnâ€™t seem to be too hard to do. No doubt, I am naive.