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 derive every law of physics?

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

You are not coming back to my questions in my comment #174. Why?

Ok. Let me jot down something, anyway.

No, I don’t think I had to invent that blackbox. However, conceptually, it’s a powerful toy, and it does help ground arguments while talking with folks who are given to taking flights into the abstract and the symbolic far too easily.

Anyway, the two main points on which _you_ are _inconsistent_, are these:

(i) You first say that G and EM are _totally_ different forces, but then you also go on to add that they _interact_.

The expression “interacting _forces_” has no meaning unless one first assumes the existence of a more basic, unifying, force. In which case, G & EM cease to be _totally_ different; they simply become two different contextual manifestations of the same underlying force. Which precisely is what I had suggested.

Tch… Do you at least now realize that all that you have actually succeeded in doing is to lend support to my position?

(ii) A different, second point. Here, you (and also many many others, including those at MIT/Berkley/Cambridge etc., those winning Nobels etc., and Indians, esp. IITians, revering all such aforementioned) may not agree. However, it’s something I believe in. BTW, it’s a direct consequence of Ayn Rand’s philosophy.

Strictly speaking, there cannot be any interaction between forces. Interactions happen between objects (entities), not between their attributes, characteristics, actions, etc. A force is nothing but a kind of an action taken by an entity. Actions (e.g. motions) do not exist independent of the entities which act.

To quote Ayn Rand: “They proclaim that there are no entities, that nothing exists but motion, and blank out the fact that motion presupposes the thing which moves, that without the concept of entity, there can be no such concept as ‘motion.’”

To suggest that two “totally different” forces can interact follows the same basic pattern as suggesting that two unrelated attributes interact. For instance, that size and texture interact. That bigness can interact with surface roughness.

So long as one is willing to drop the context and blank out necessary facts, one can always come up with a lot of argumentation, perhaps an intelligent one, perhaps a socially satisfying one, perhaps one that leads to money, perks and career advancements, etc. Perhaps. But, always, ultimately, in rebellion against reality.

If I were in your place, rather than writing a new blog post involving interaction, I would have come back and on my own clarified this point—viz., that I had smartly, almost cheatingly, slipped in that interaction thingie in that argument above. And, I would have agreed that all the G + QM programs are at best only tentative in nature.

Tch. Berkeley/MIT/etc. folks. Remarkably like IITians. No point expecting such things from them.

Ajit
[E&OE]