I’ve been working on an alternative to MWI that also includes information restrictions for local mechanisms in a quantum universe (like an observer). The constrains come from interaction locality, and while sharing the starting point with MWI, they lead to a very different picture. My blog contains a gentle introduction to the approach and a pointer to more rigorous explanations: http://aquantumoftheory.wordpress.com/2012/09/12/does-quantum-theory-have-to-be-interpreted/

]]>The post asserts that either QM “goes all the way” and allows macroscopic cat states and other counter intuitive scenarios or that there is some theory of forced decoherence that kick in in the macroscopic scale, and Scott (for having no clear opinion) gives 50:50 chance for each possibility. My questions are:

1) Is MWI the only interpretation which support QM going “all the way?”. E.g., why not to think about QM as a mathematical theory of noncommutative probability as (if I understood him correctly) Steve Landsburg suggests #46 .

2) Cat states are fairly simple. Why to regard macroscopic cat states as harder to get than the very entangled states we see in quantum algorithms of quantum error correction?

3) Isn’t it more likely to think that the distinction between microscopic/macroscopic systems emerges from the physics rather than that there will be different a priori principles for microscopic and macroscopic systems?

4) The way I look at it a theory of decoherence (or noise) is simply a theory of approximation of large quantum systems when you neglect some (or many) degrees of freedom. Viewed this way many computational methods in quantum physics can be seen as such approximation recipes. Are such approximation methods expected (or even known) to follow “from first principles” from the basic framework of QM or rather to supplement it?

5) A related question: Should we regard QM as a mathematical language that allows to ** express** every law of physics or rather more strongly as a theory that allows to

6) Of course, the case of thermodynamics in the context of question 5 is especially interesting. What about thermodynamics?

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