Retrocausal Models in Quantum Mechanics
The mini-conference will be held in the Main Quadrangle Refectory (downstairs in the SW corner).
Click on titles for abstracts.
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10:00 - 11:00 11:40 - 12:40 14:20 - 15:20 15:20 - 16:20 17:00 - 17:30
17:30 - 18:00 |
Retrocausality
and Ehrenfest's theorem
David Miller (Centre for Time)
An expression is proposed for incorporating initial and final states (or boundary conditions) into calculating expectation values of (unmeasured) quantities like momentum and position in quantum mechanics. It is shown that Ehrenfest's theorem still holds and the consequences of Ehrenfest's theorem for some examples show how the proposed expression seems to lead to more intuitively satisfying results than standard quantum mechanics. The Wigner distribution corresponding to the proposed expression is also discussed. The theory is applied to examples which are said to lead to 'surreal' trajectories in the case of Bohmian mechanics.
Replacing
Amplitudes with Probabilities
Rod Sutherland (Centre for Time)
A natural extra assumption to
propose when considering the interpretation of quantum mechanics is
that a particle still has a definite position when we are not looking,
i.e., in the absence of a position measurement being performed. An
immediate consequence of making this assumption, however, is the
following: When an ensemble of independent particles in a particular
initial state can reach a final state via several different paths,
there will be definite, albeit hidden, frequencies of occurrence for
the different routes, i.e., a definite probability for each path. For
the case where no attempt is made to detect each particle’s path, the
formalism of quantum mechanics does not provide such individual
probabilities. Instead, it provides us with amplitudes to be added to
obtain the overall probability. In this talk I will formulate a simple
rule that gives an apparently viable set of probabilities for every
situation and examine the acceptability and implications of this rule.
This alternative formalism has the advantage of being equally
applicable in all versions of quantum theory from non-relativistic
particles through to relativistic quantum field theory.
This approach is an extension of the
“causally symmetric” Bohm model I have employed as an example in
previous discussions
The
Klein-Gordon equation as a time-symmetric generalization of the
Schroedinger equation
K.B. Wharton (SJSU) and Eric Cavalcanti (Griffith)
Paper available here.
Erwin
Schrodinger derived his non-relativistic wave equation from the
covariant Klein-Gordon equations (KGE), and dropped half the solutions
of the KGE in the process. These so-called "negative energy
solutions" have no reasonable interpretation in standard quantum
mechanics, but provide a natural doubling of the solution space,
allowing one to impose a second boundary condition and still find
general solutions. We propose to impose an additional final
boundary condition (corresponding to a measurement) on the full KGE
wave equation. The solution to the KGE between the two boundaries is
then reinterpreted as a realistic wavefunction that symmetrically
depends on both past and future events.
Retrocausality
in consistent histories models
Peter Lewis (Miami)
I develop a simple model based on Gell-Mann and Hartle's many-histories formalism. This model deals with Barrett's worries about the many-histories approach by picking a preferred history-hence it is essentially a hidden variable theory. However, it is not clear what the hidden variables in this model should be taken to be. I show that on one specification of what the hidden variables are, the model violates Locality and satisfies Independence, but on another specification, it satisfies Locality and violates Independence. The latter specification yields a model that is (arguably) retrocausal. I speculate about whether we should regard these two specifications as yielding distinct hidden variable theories.
Maudlin's
objection to retrocausality
Pete Evans (Centre for Time)
In response to the transactional interpretation of quantum mechanics due to John Cramer, Tim Maudlin has levelled an objection at retrocausal models of quantum mechanics. Maudlin claims that his objection to the transactional interpretation poses a problem for "any theory in which both backwards and forwards influences conspire to shape events". At the time this claim was made, the transactional interpretation was the only substantially developed retrocausal model. The development of further retrocausal models in recent years has opened the way for testing Maudlin's objection against varying retrocausal mechanisms. I will present a detailed characterisation of the objection with specific reference to the transactional interpretation of quantum mechanics. I then wish to review Maudlin's objection in the light of some more recent retrocausal models with a view to showing that Maudlin's objection is specific to Cramer's transactional interpretation.
Alice
through the hour-glass
Guido Bacciagaluppi (Centre for Time)
This talk reports on some work very much in progress on the analysis of bipartite experiments in which Alice has the opposite arrow of time to Bob.
Retrocausal
Toy Models
Huw Price (Centre for Time)
I introduce a simple retrocausal toy model, intended to illustrate some of the likely features of grownup retrocausal models of QM.
Enquiries to Guido Bacciagaluppi.
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Last Update
20/11/07