On 10/26/2013 10:21 AM, Jason Resch wrote:

Brent,## Advertising

Section 3b of ( http://arxiv.org/pdf/quant-ph/9709032v1.pdf ) seems to also answer someof the questions you posed recently regarding superposition in MWI:B. “It doesn’t explain why we don’t perceive weird superpositions” That’s right! The Everett postulate doesn’t! Since the state corresponding to a superposition of a pencil lying in two macroscopically different positions on a table-top is a perfectly permissible quantum state in the MWI, why do we never perceive such states? The inability to answer this question was originally a serious weakness of the MWI, which can equivalently be phrased as follows: why is the position representation so special? Why do we perceive macroscopic objects in approximate eigenstates of the position operator r and the momentum operator p but never in approximate eigenstates of other Hermitian operators such as r + p? The answer to this important question was provided by the realization that environment-induced decoherence rapidly destroys macrosuperpositions as far as the inside view is concerned, but this was explicitly pointed out only in the 70’s [12] and 80’s [13], more than a decade after Everett’s original work. This elegant mechanism is now well-understood and rather uncontroversial [14], and the interested reader is referred to [15] and a recent book on decoherence [16] for details. Essentially, the position basis gets singled out by the dynamics because the field equations of physics are local in this basis, not in any other basis. If you do not find this answer satisfying, I would be interested to know why. Thanks.

`I'm familiar with that answer. It's the same one Schlosshauer considers in his review`

`paper. But he also notes that atoms, for example, are found in energy eigenstates - not`

`position eigenstates (in spite of the EM field also be "local"). More generally the basis`

`is supposedly "ein-selected" by being the basis whose interaction Hamiltonian with the`

`environment is robust against perturbations.`

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