Exploring the Fundamental Postulates of QM: Are They Truly Ad-Hoc and Strange?

[bhobba]

What do you mean by a fully quantum theory of measurement, if QM isn't one already? (Keep in mind that QM includes decoherence). And what is it required for?

A theory of measurement that does not include the a priori existence of classical measurement devices like Copenhagen does. It is only of recent times such theories have emerged - but as yet have not been full worked out eg my understanding is that the emergence of a classical domain from QM is not quite 100% complete - we are almost there - but not quite - at least that's what I have read.

The von Neumann regress, if you mean what I think you mean, doesn't have anything to do with the consciousness causes collapse idea. The former is just the observation about what a theory is, and the latter is at best a wild speculation about reality.

Von Neumann was one of the first, or maybe even the first, to examine the measurement process fully quantum mechanically. What that showed is where the wavefunction collapse occurs could be placed anywhere and if we keep following it all the way back to the observer it is only at consciousness something different comes into it. To some such as Wigner this is where they placed the collapse:
http://en.wikipedia.org/wiki/Interp...rpretation:_consciousness_causes_the_collapse

'In his treatise The Mathematical Foundations of Quantum Mechanics, John von Neumann deeply analyzed the so-called measurement problem. He concluded that the entire physical universe could be made subject to the Schrödinger equation (the universal wave function). He also described how measurement could cause a collapse of the wave function. This point of view was prominently expanded on by Eugene Wigner, who argued that human experimenter consciousness (or maybe even dog consciousness) was critical for the collapse, but he later abandoned this interpretation'

I have an aged copy of Von Newmann's text, and while it been years since I have read it (its actually one of the first books I learned QM from because it was mathematically more in line with the Hilbert spaces I studied in my math degree - other texts were not quite as transparent to me until I learned a bit about Rigged Hilbert Spaces - but that is another issue) I seem to recall that's pretty much what he did.

Wigner abandoned it when he heard of some early work on decoherence by Zurek.

I think the idea that the basis is independent of the decomposition is as likely to be true as the idea that 2x is independent of x.

And you may be right - however I prefer not to be so sure about it until the theorems demonstrating it unequivocally one way or another are forthcoming and they have had time to be checked. It is interesting standard texts on dechorenece such as the one I have make no mention of it - there may be something already known about it we are missing - I am adopting a wait and see attitude to it..

Thanks
Bill