Clarifications requested from audience. Speaker agrees: decoherence does not select a given quantum states, so it does not coincide with the measurement process. It only gives a physical mechanism for understanding the suppression of interference. In particular, it explains why we do not observe superpositions and interference of macroscopic objects. More discussion with the audience about this point.

Set aside, for present purposes, in particular for studying physical problems, the issue of interpretation. The focus here is on the specific physical process corresponding to measurement, and the way it suppresses superposition of quantum states.

General definition of decoherence, as due to entanglement between system and environment, leading to the appearance of classical or quasi-classical description of the same system. Not an interpretation of quantum mechanics, even though it plays an important role in several interpretations of quantum mechanics. It is a physical process.

Stressing the importance of decoherence in quantum mechanics in general, and of the interest in studying it in the context of quantum gravity.

The Role of Decoherence in Quantum Loop Dynamics

CW stresses that locality of spin network structures and captured by connectivity of these networks is very different from locality of relativistic STs.  Something very distinct is going on here…

CONCLUSION: classical space and time seem to disappear in canonical q grav, and they might re-emerge from fundamental non-ST structure. 

Worry here is that states in superpositions generally don’t have connectivity [and perhaps have different cardinality].  Not obvious what the dimensionality of these fundamental structures must be, then.

Another issue involves locality structure arising from emergent ST described via LQG approach.  I.e., how local or topological structures like relativistic STs emerge from spin networks.  This will be key for q cosmological investigations…

Moving on to the problem of ST in LQG: Hamiltonian formulation of GR in an attempt to apply canonical quantization; belief is that resultant Hilbert basis is spin network basis, and these spin networks provide the fundamental 3-d spatial structure [and these networks can be considered eigenstates of geometrically-interpreted operators]

Thus: space comes out as superposition of spin network eigenstates — i.e., no well-defined geometric properties

Nota bene: the sort of indeterm at issue here has to do specifically with the indeterm arising from requirement of diffeomorphism invariance

Question: when you have vel-dep coord transformations, you should work with a phasespace across time.  This would not be implement-able in a reduced phasespace of the sort proposed by Maudlin.  CW responds: neither Maudlin nor I claim this will lead to solution to the problem, but may alter the way we view it..