On 1/2/2014 10:38 PM, Jason Resch wrote:
On Fri, Jan 3, 2014 at 12:20 AM, meekerdb <[email protected]
<mailto:[email protected]>> wrote:
On 1/2/2014 7:37 PM, Jason Resch wrote:
On Thu, Jan 2, 2014 at 8:35 PM, LizR <[email protected]
<mailto:[email protected]>>
wrote:
On 3 January 2014 14:31, meekerdb <[email protected]
<mailto:[email protected]>> wrote:
Then I'll start by saying I don't reject MWI, I just have
reservations
about it, not so much that it's wrong, but that it doesn't really
solve the
problems it claims to - which implies criticism of the position
that MWI
has solved all the problems of interpreting QM. A lot of the above
claimed
advantages knocking down straw men built on naive interpretations of Bohr.
Some are just assumptions, e.g that physics must be time reversible and linear.
I thought linearit was probabilities adding up to one, which isn't a
radical
assumption???
I think you might be thinking of unitary vs. non-unitary:
http://en.wikipedia.org/wiki/Unitarity_(physics)
<http://en.wikipedia.org/wiki/Unitarity_%28physics%29>
Time reversibility is an observed phenomenon in (almost) all particle
interactions, so surely not an assumption at all?
I agree, things like CPT symmetry, determinism, etc. aren't just
assumptions, but
underlie every other known physical law that is known.
http://en.wikipedia.org/wiki/CPT_symmetry
The *CPT theorem* says that CPT symmetry holds for all physical phenomena,
or more
precisely, that any Lorentz invariant
<http://en.wikipedia.org/wiki/Lorentz_invariant> local quantum field theory
<http://en.wikipedia.org/wiki/Quantum_field_theory> with a Hermitian
<http://en.wikipedia.org/wiki/Self-adjoint_operator>Hamiltonian
<http://en.wikipedia.org/wiki/Hamiltonian_%28quantum_mechanics%29> must
have CPT
symmetry.
Collapse of the wave function would be the only phenomenon in quantum
mechanics
that is non-unitary, non-linear, non-differentiable, and discontinuous. It
would
also be the only principle in physics that non-local, non-causal,
non-deterministic, and violates special relativity.
I can understand that Brent's ambivalence toward MWI, it may not be the
final
answer, but I think it is a good step in that direction. However, I am
surprised
that anyone well-versed in the known physics of today, could consider
collapse as
anything but a wild, unsupported, and almost-certainly-false conjecture.
That's what I mean by attacking a straw man. Fuchs and Peres et al,
including Bohr
only considered 'collapse of the wave function' as a change in one's
information.
I agree Bohr was closer to Fuchs and Peres, but Heisenberg, von Neumann, Wigner, etc.
all believed in collapse, and CI is still taught as the orthodox interpretation in most
places. It's not exactly a straw man.
To say the theory is only about our information seems like a kind of cop-out to me. We
don't see other theories in science described as only speaking about the information
that we can gain not about anything that real external to us. Why can't QM be a realist
theory like everything else in science?
I sort of see the opposite trend. More and more physicists are looking for an information
based fundamental theory.
Bohr said QM is not about reality, it's about what we can say about
reality. Only
later did people try to invent real collapse theories, e.g. Penrose, and
while I
don't consider any of them likely I wouldn't say they are almost certainly
false.
Let's say someone proposed a new theory to explain why when something falls into a black
hole we can no longer see it, but it ignored that other theories already explain why we
can't see things that fall into a black hole.
Or how about a theory that it's both destroyed at the event horizon and also falls through
to the singularity?
Moreover, imagine that this theory, if true, would require faster than light influences,
as well as violations in the second law of thermodynamics and conservation of mass
energy. Would you say this theory was only "unlikely"?
Are you claiming that Penrose's idea does all those things?
There is so much well-established physics that must be given up; for
apparently no
other reason than the ontological prejudice some harbor for the idea that
the
universe is no bigger than we previously thought.
That's as good a prejudice as every thing must be determined from the
beginning.
Now who is fighting straw men? (You always pretend this this is the primary, or only
motivation for Everett)
I don't know about you, but Bruno has said he considers fundamental randomness to be
completely unacceptable. What do you think about the idea that the whole course of the
universe was set at that (near) singularity at the beginning of the universe? I realize
it was probably not Everett's motivation - he was more interested in the Heisenberg cut
problem.
Brent
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