On 7 Oct 2012, at 07:54, David <davids...@gmail.com
> I was just reading some of the chapters from the upcoming book "The Wavefunction" by David Z. Albert where several different authors make their case for/against wavefunction realism and discuss the ontology of the WF in general.
> We all know that the Everettian interpretation is very much "The WF is all there is", but David Wallace and Chris Timpson think that the standard "WF realism" is untenable and that it should be replaced by space-time state realism.
> I was just wondering: which view is the fungible worlds ?
I haven't read Albert's book, nor the Wallace-Timpson argument you're referring to. So I don't know what exactly they mean by 'wave function realism' or 'space-time state realism'.
But in any case, 'wave function realism' must be a telescoped term. "The wave function is real", though often used as a slogan to express realism in quantum theory, can't literally mean that reality consists of a certain function (a mapping from some exponentially large configuration space to the complex numbers). To make any sense, it must refer to the view that every mathematical property of the wave function (to be exact: every property except the overall phase) describes, or corresponds to, some property of the real, physical world.
All forms of the Everett interpretation (and also one half of the Bohm-interpretation equivocation) agree on that.
However, the wave function is a mathematical object used in the Schrödinger picture, in which information flow, and hence the structure of the multiverse, is expressed in a highly indirect, implicit way that has caused endless misunderstanding, especially the myth of quantum non-locality. In the Heisenberg picture, in which information flow is represented explicitly, it is manifestly local too. The state of the Heisenberg observables is then what corresponds to reality, and they are local functions on space-time. If that's what's meant by space-time realism, I'm all for it.
Fungibility is part of my attempt to explain what the multiverse is actually like, and should therefore be picture-independent.
-- David Deutsch