On 30/05/2017 7:28 pm, Telmo Menezes wrote:
On Tue, May 30, 2017 at 3:47 AM, Pierz <pier...@gmail.com> wrote:
So you are talking different
languages.
Not sure I agree. We are perhaps implicitly assuming different theories of mind.
I don't know if Telmo is aware or not of the conventional view of
decoherence - that it is a matter of the spread of information into the
environment by means of physical interactions between particles. Telmo's
musings about the effect of destroying memory (could it change the measure
of different futures?) clearly expresses this subjectivist view.
I get your point with decoherence.
Again, I would say that it all depends on theories of mind. What does
mind supervene on? Perhaps it is true that every single coupling with
the environment prevents the current observer state to become
compatible with other branches. But can we be sure? I feel that such
certainties come from a strong belief in emergentism (which I cannot
disprove, but find problematic).
FWIW, you
are expressing my own understanding of the situation: there can be no
superposition of red and green screens or dinosaurs, or dead and live cats,
because there can be no quantum superposition of macroscopic objects.
Superpositions of wave functions are only possible for systems isolated from
interaction with their environment, which is why quantum computers are so
fricking hard to make: keeping aggregates of particles isolated from
interactions with the surrounding environment is exponentially more
difficult as the system grows in size.
The main question for me is this: can two branches hold different
observer states, if they differ only by things that are not
observable?
Yes, but I think we should be talking about quantum mechanics here, and
that is a well-defined physical theory that is not really concerned with
any theory of mind. There have been some interpretations of quantum
mechanics that ascribe the mind a role in the collapse of the wave
function, or some such; and some who re-interpret the many worlds idea
as a 'many minds' picture; but these issues do not seem to be relevant
to any discussion of the quantum formalism itself.
In the discussions on this list, it seems that MWI is the dominant
understanding of QM. That is fine, one can certainly talk about things
in this way. But it should be borne in mind that MWI is actually
equivalent to the less well known decoherent histories approach. I guess
that in my comments earlier in this thread, I was emphasizing the
decoherent histories understanding. In many worlds, worlds separate off
when irreversible interactions with the environment zero out the
interference terms between different elements in the superposition. This
happens inevitably all the time, and measurements, or observers, play no
essential role in the process. Each world of the MWI is thus produced by
the process of decoherence acting on the initial quantum state. Each
decoherent line then evolves on to produce its own set of future
decoherent lines. Following through any particular line gives a
decoherent history -- one for each world of the MWI.
Since the processes of decoherence and the formation of histories or
worlds are independent of the observer and of the mind, it is clearly
possible that different branches (or histories) can differ only by
things that are not observed, or even not observable. And this is just a
matter of the formalism of quantum mechanics -- it has nothing to do
with any theory of mind. The only thing that I would say, though, is
that your theory of mind, and your theory of the origin of physics, must
be compatible with this understanding of quantum mechanics -- or else
your theory of mind/physics is falsified.
Bruce
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