On 3/1/2015 1:00 PM, LizR wrote:
On 27 February 2015 at 16:20, Bruce Kellett <bhkell...@optusnet.com.au
<mailto:bhkell...@optusnet.com.au>> wrote:
Jason Resch wrote:
There's no problem defining probability. There is, however, a big
problem
defining collapse.
Collapse is easily defined. No one has yet given an adequate account of
probability
within the Everettian program. Branch counting is known not to work, but
neither
does anything else!
What I don't see is how collapse has less of a problem with the Born rule than the MWI.
They are identical except the MWI doesn't discard the other possibilities. If the MWI
has a problem deriving probability of an outcome from an infinite number of
possibilities, then why doesn't collapse?
The difference is only that MWI pretends not to need anything else, that evolution of the
SWE accounts for everything. That's what makes it a better theory - fewer assumptions.
Explicit collapse theories add it as a different physical process. These get confused
with "Copenhagen" interpretations like Peres and quantum bayesianism in which the SWE is
just a computational device and its "collapse" is just revising what you know when you get
the experimental result.
I put "Copenhagen" in scare quotes because the name is most associated with Bohr, but Bohr
didn't think of collapse of the wave function as a physical process. He said, "Physics is
not about the world, but about what we can say about the world." He emphasized that
scientific knowledge existed only in the classical world where there were records that
could be objectively agreed on. He had a kind of mystic quantum/classical dualism and he
tried to extend complementarity to things outside physics. Heisenberg disliked this and
regarded complementarity as a simple consequence of measurement perturbing the system.
Brent
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