Open thread, August 5-11, 2013

David_Gerard

If it's worth saying, but not worth its own post (even in Discussion), then it goes here.

I wouldn't call Everett 'Anthropic' per se. I consider it an application of the Generalized Anti-Zombie Principle: Here you've got this structure that acts like it's sapient†. Therefore, it is.

As for BM formally specifying how the reality fluid works... need I point out this this is 100% entirely backwards, being made of burdensome details?

Would you say that acknowledging the Born probabilities themselves 'comes out of the blue', since they aren't derived from the Schrödinger equation?

The Schrödinger Equation establishes linearity, thus directly allowing us to split any arbitrary wavefunction however we please. Already we can run many worlds side-by-side. The SE's dynamics lead to decoherence, which makes MWI have branching. It's all just noticing the structure that's already in the system.

Edited to add †: by 'acts like' I mean 'has the causal structure for it to be'

The Schrödinger Equation establishes linearity, thus directly allowing us to split any arbitrary wavefunction however we please.

But many of the more-general lagrangians of particle physics are non-linear, in general there should be higher order, non-linear corrections. So Schrödinger is a single-particle/linearized approximation. What does this do for your view of many worlds? When we try to extend many worlds naively to QFTs we run into all sorts of weird problems (much of the universal wavefunction's amplitude doesn't have well defined particle number,etc). Shouldn't we expect the 'proper' interpretation to generalize nicely to the full QFT framework?

0Rob Bensinger13y

I'm not sure what you mean by 'anthropic per se'. Everett (MW) explains apparent quantum indeterminism anthropically, via indexical ignorance; our knowledge of the system as a whole is complete, but we don't know where we in the system are at this moment. De Broglie (HV) explains apparent quantum indeterminism via factual ignorance; our knowledge of the system's physical makeup is incomplete, and that alone creates the appearance of randomness. Von Neumann (OC) explains apparent quantum indeterminism realistically; the world just is indeterministic. [...] This is either a very implausible answer, or an answer to a different question than the one I asked. Historically, the Born Probabilities are derived directly from experimental data, not from the theorized dynamics. The difficulty of extracting the one from the other, of turning this into a single unified and predictive theory, just is the 'Measurement' Problem. Bohm is taking two distinct models and reifying mechanisms for each to produce an all-encompassing theory; maybe that's useless or premature, but it's clearly not a non sequitur, because the evidence for a genuine wave/particle dichotomy just is the evidence that makes scientists allow probabilistic digressions from the Schrödinger equation. MW is not a finished theory until we see how it actually unifies the two, though I agree there are at least interesting and suggestive first steps in that direction. BM's costs are obvious and clear and formalized, which is its main virtue. Our ability to compare those costs to other theories' is limited so long as it's the only finished product under evaluation, because it's easy to look simple when you choose to only try to explain some of the data.

-4Shmi13y

That's just regurgitating the teacher's password. MWI does not even account for the radioactive decay. In other words, if you find the Schrodinger's cat dead, how long has it been dead for?

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