The great success of the Decoherence program is the debunking of the mind
causes Quantum wave collapse. Nothing we know puts this success in any
jeopardy. Nevertheless a landmark paper by Dowker and Kent would seem to force
us to bring the subjective back into the measurement problem.
Abstract: We review the consistent histories formulations of quantum
mechanics developed by Griffiths, Omn\`es and Gell-Mann and Hartle, and describe
the classification of consistent sets. We illustrate some general features
of consistent sets by a few simple lemmas and examples. We consider
various interpretations of the formalism, and examine the new problems which
arise in reconstructing the past and predicting the future. It is shown that
Omn\`es' characterisation of true statements --- statements which can be
deduced unconditionally in his interpretation --- is incorrect. We examine
critically Gell-Mann and Hartle's interpretation of the formalism, and in
particular their discussions of communication, prediction and retrodiction, and
conclude that their explanation of the apparent persistence of
quasiclassicality relies on assumptions about an as yet unknown theory of experience.
Our overall conclusion is that the consistent histories approach illustrates
the need to supplement quantum mechanics by some selection principle in
order to produce a fundamental theory capable of unconditional predictions.
Abstract: We consider notions of physical equivalence of sets of histories
in the quantum mechanics of a closed system. We show first how the same
set of histories can be relabeled in various ways, including the use of the
Heisenberg equations of motion and of passive transformations of field
variables. In the the usual approximate quantum mechanics of a measured
subsystem, two observables re- presented by different Hermitian operators are
physically distinguished by the different apparatus used to measure them. In the
quantum mechanics of a closed system, however, any apparatus is part of
the system and the notion of physically distinct situations has a different
character. We show that a triple consisting of an initial condition, a
Hamiltonian, and a set of histories is physically equivalent to another triple
if the operators representing these initial conditions, Hamiltonians, and
histories are related by any fixed unitary transformation. We apply this
result to the question of whether the universe might exhibit physically
inequivalent quasiclassical realms (which we earlier called quasiclassical
domains), not just the one that includes familiar experience. We describe how the
probabilities of alternative forms, behaviors, and evolutionary histories
of information gathering and utilizing systems (IGUSes) using the usual
quasiclassical realm could in principle be calculated in quantum cosmology,
although it is, of course, impractical to perform the computations. We discuss
how, in principle, the probabilities of occurence of IGUSes could be
calculated in realms distinct from the usual quasiclassical one. We discuss how
IGUSes adapted mainly to two different realms could draw inferences about
each other using a hybrid realm consisting of alternatives drawn from each.
The problem identified by Dowker and Kent is that the Decoherent histories
that produce our classical Universe are but a subset of the total number
of Decoherent histories produced in the Decoherent process. The response of
Hartle and Gell Mann is that the reduced subset of quasi classical
histories are the result of the evolution process which selected for
predictability. If correct this has profound implications for our understanding of
reality. Based on this einselection would be the first step but the subjective
processes of our sensory neurological system is needed to produce the
classical world we observe. That is, perception provides only a useful subset of
reality. How, this might work in detail is unknown and this invites
reasonable skepticism.
Nevertheless, the subjective nature of the Quantum measurement process has
always been an unwanted part of the ansatz of the measurement process. And
it should be noted that this is no way lends support to the mind causes
collapse view, though it does lend support to the possibility that the mind
created reality is subjective at its core.
Of course this subjective creation of reality must relate in a useful way
to nature or we wouldn't be here to talk about it. Zurek writes:
"Our Senses did not evolve for the purpose of verifying Quantum
mechanics, Rather, they have developed in the process in which survival of the
fittest played a central role. There is no evolutionary reason for perception
when nothing can be gained from prediction. And as the predictability sieve
illustrates, only Quantum states that are robust in spite of Decoherence,
and hence, effectively classical, have predictable consequences. Indeed,
classical reality can be regarded as nearly synonymous with predictability."
End quote
In any Quantum measurement you can divide the total measurement system
into
1)The Subject which consist of the degrees of freedom associated with the
subjective perception of the observer.
2) The Object which consist of the degrees of freedom of that the observer
is interested in, the pointer position on the measurement apparatus.
3) The Environment which are the degrees of freedom of everything else in
the interaction process, those degrees of freedom that the observer
ignores.
This give us the total Decoherence Hamiltonian of
H_dec= H_se + H_so + H_oe
Given a pure state
Y= SUM { all i} c_i*Y*i
Which gives us
Y=SUM {all i} c_i*{ Y_i X Y_s X Y_e X Y_o }
Here you can't separate the Observer degrees of freedom in any measurement
we can be aware of, obviously.
Zeh makes the case that this leads to the Many Minds Interpretation of
Quantum Mechanics. Schlosshauer writes (Decoherence and the Quantum to
Classical Transition" )
Other Authors such as Zeh have suggested that the empirical fact of
decohering wave functions components in neuronal processes constitute sufficient
(if not compelling) grounds for postulating, within the Quantum mechanical
formalism, the existence of consciousness" In this picture, dynamically
autonomous conscious observers are then associated with the robust components
of the global wave function of the type:
SUM { all n} c_n* [n> X [Apparatus> X [Obs ready> to
SUM { all n} c_n* [n> X [pointer set > X [Obs sees pointer>
With each of the components of the labeled by the decohered neuronal
states corresponding to definite resting/firing patterns. We thus obtain a
multitude of classical worlds (defined by robust branches) within a single
Quantum Universe. ( Described by the Unitarily evolving global Quantum State
Vector.)
The conjecture is then that, because the different conscious versions of
the observer would be aware of each other, from the inside (frog)
perspective of the observer one should be able to account for the empirically
required perception of definite measurements outcomes, without relinquishing the
assumption that Quantum states describe (some form of) physical reality and
that Unitary dynamics is Universally valid."
End Quote
This view is a modified form of Psycho-Parallelism , rather than an
idealistic ontology. An essentially monist answer to the matter mind question.