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## Main Question or Discussion Point

Demystifier has a paper available entitled "Quantum mechanics: myths and facts". http://xxx.lanl.gov/abs/quant-ph/0609163 This is a fine overview of a lot of stuff which I would like to understand better. Please join me in discussing.

There are 9 myth categories. By myth the author means widely repeated statements which, true or false, are not something we can validly assert given our current understanding.

The gist of section 2.1 is that based on the usual interpretation of QM, there is only the wave. What we call particle is merely the special case of a localized wave packet--of finite width and only ideally a delta function in the limit of [tex]\Delta x \rightarrow 0[/tex].

I have two tentative objections.

(1) The single particle wave function [tex]\psi (x,t)[/tex] can be misleading. It suggests something like an EM wave or a fluid wave. That is, a field, a value at each point in physical space at a given time. But this is wrong of course. For two particles we don't have [tex]\psi_1(x,t)[/tex] and [tex]\psi_2(x,t)[/tex] (although that may be approximately true if they don't interact) but rather [tex]\psi (x_1, x_2; t)[/tex]. The wave function lives in configuration space not physical space. Hence, it is not physically real but instead only a calculational tool.

That is, unless we are willing to grant configuration space a sort of platonic reality that is more real than the physical world that we experience with our senses. A logical possibility of course. The world of normal space time of our experience may merely be the result of how our brains+senses fit in as part of the universal wave function. In that case one could say that the wave function is the reality and it is the world of our experience which is the "calculational tool" provided to us by evolution for survival.

But this is a position of which I think we should be very suspicious. The most glaring problem with it in my opinion is the "measurement problem" and the fact that we don't observe superposition of macro objects, a fact for which the wave function alone has no answer. And for other reasons which will come up as we discuss the "myths".

(2) Particle position plays such a central role in actual measurements. I have heard it said that

This suggests to me that the usual formulation of QM is only an approximation and that a better theory would be a particle theory. And indeed, in Sec 2.2 Demystifier discusses such a possibility in the Bohmian interpretation.

But what do we even mean by "particle"? I have to admit that at this level I have better mental grasp of the wave function than what a "particle" is or might be.

There are 9 myth categories. By myth the author means widely repeated statements which, true or false, are not something we can validly assert given our current understanding.

**myth category 1. Wave particle duality**(see section 2 of the paper)The gist of section 2.1 is that based on the usual interpretation of QM, there is only the wave. What we call particle is merely the special case of a localized wave packet--of finite width and only ideally a delta function in the limit of [tex]\Delta x \rightarrow 0[/tex].

I have two tentative objections.

(1) The single particle wave function [tex]\psi (x,t)[/tex] can be misleading. It suggests something like an EM wave or a fluid wave. That is, a field, a value at each point in physical space at a given time. But this is wrong of course. For two particles we don't have [tex]\psi_1(x,t)[/tex] and [tex]\psi_2(x,t)[/tex] (although that may be approximately true if they don't interact) but rather [tex]\psi (x_1, x_2; t)[/tex]. The wave function lives in configuration space not physical space. Hence, it is not physically real but instead only a calculational tool.

That is, unless we are willing to grant configuration space a sort of platonic reality that is more real than the physical world that we experience with our senses. A logical possibility of course. The world of normal space time of our experience may merely be the result of how our brains+senses fit in as part of the universal wave function. In that case one could say that the wave function is the reality and it is the world of our experience which is the "calculational tool" provided to us by evolution for survival.

But this is a position of which I think we should be very suspicious. The most glaring problem with it in my opinion is the "measurement problem" and the fact that we don't observe superposition of macro objects, a fact for which the wave function alone has no answer. And for other reasons which will come up as we discuss the "myths".

(2) Particle position plays such a central role in actual measurements. I have heard it said that

*all*measurements ultimately reduce to positions measurements. (But is this one more myth?)This suggests to me that the usual formulation of QM is only an approximation and that a better theory would be a particle theory. And indeed, in Sec 2.2 Demystifier discusses such a possibility in the Bohmian interpretation.

But what do we even mean by "particle"? I have to admit that at this level I have better mental grasp of the wave function than what a "particle" is or might be.