[ExI] Broken Time Translation Symmetry and State Reduction

[Damien Broderick]

This might interest some here (Serafino?):

<http://arxiv.org/abs/0912.4202>

Broken Time Translation Symmetry as a model for Quantum State Reduction
Authors: Jasper van Wezel
(Submitted on 21 Dec 2009)

    Abstract: The symmetries that govern the laws of nature can be 
spontaneously broken, enabling the occurrence of ordered states. 
Crystals arise from the breaking of translation symmetry, magnets from 
broken spin rotation symmetry and massive particles break a phase 
rotation symmetry. Time translation symmetry can be spontaneously broken 
in exactly the same way. The order associated with this form of 
spontaneous symmetry breaking is characterised by the emergence of 
quantum state reduction: systems which spontaneously break time 
translation symmetry act as ideal measurement machines. In this review 
the breaking of time translation symmetry is first compared to that of 
other symmetries such as spatial translations and rotations. It is then 
discussed how broken time translation symmetry gives rise to the process 
of quantum state reduction and how it generates a pointer basis, Born's 
rule, etc. After a comparison between this model and alternative 
approaches to the problem of quantum state reduction, the experimental 
implications and possible tests of broken time translation symmetry in 
realistic experimental settings are discussed.

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A commentator notes: "Broken time translation symmetry is code for 
non-unitarity, of course." Which is usually regarded as a no-no.

Damien Broderick