It seems that there’s now a new burgeoning field bringing together multiverse studies and interpretational issues in quantum mechanics. Last year Aguirre, Tegmark and Layzer came out with with Born in an Infinite Universe: a Cosmological Interpretation of Quantum Mechanics, which claimed:
This analysis unifies the classical and quantum levels of parallel universes that have been discussed in the literature, and has implications for several issues in quantum measurement theory… the analysis suggests a “cosmological interpretation” of quantum theory in which the wave function describes the actual spatial collection of identical quantum systems, and quantum uncertainty is attributable to the observer’s inability to self-locate in this collection.
Last month there was Nomura’s Physical Theories, Eternal Inflation, and Quantum Universe where “a picture that the entire multiverse is a fluctuation in the stationary, fractal “mega-multiverse,” in which an infinite sequence of multiverse productions occurs” is invoked and:
Our framework provides a fully unified treatment of quantum measurement processes and the multiverse. We conclude that the eternally inflating multiverse and many worlds in quantum mechanics are the same.
Most recently, tonight’s arXiv listing has Bousso and Susskind’s The Multiverse Interpretation of Quantum Mechanics:
We argue that the many-worlds of quantum mechanics and the many worlds of the multiverse are the same thing, and that the multiverse is necessary to give exact operational meaning to probabilistic predictions from quantum mechanics.
I confess that I’m having trouble making sense of any of these papers. According to Bousso and Susskind, if I want to understand how quantum mechanics describes some simple, local physical system and what happens when I do measurements of it, I need to sign on to the theory of eternal inflation and the multiverse:
We will offer some principles that we believe are necessary for a consistent interpretation of quantum mechanics, and we will argue that eternal inflation is the only cosmology which satisfies those principles.
In the case of many string theory papers, one’s problems understanding their claims could often be attributed to the highly complex and sophisticated mathematical framework involved. These papers are mostly long sections of verbiage, sometimes with pictures. My inability to make sense of them must have some other source…
Update: Lubos has an explanation of the Bousso-Susskind paper: “they’re on crack”.
Update: I suppose one could have guessed that Sean Carroll would be a fan of this. In his book he argues that the way to understand the second law of thermodynamics and the arrow of time is to invoke cosmology and the multiverse, now he seems happy to do the same thing with the interpretation of quantum mechanics. The ideas seems to be that to understand some local quantum mechanical phenomenon, you need to use cosmology and think about the horizon that is part of the deSitter geometry. I don’t find this argument any more plausible than the arrow of time one.
It does seem like this is now being promoted as the hot topic in theoretical physics, with Sean and others organizing a conference partially devoted to this at Perimeter this summer.