----- Original Message ----- 
From: "Brent Meeker" <[EMAIL PROTECTED]>
To: "Saibal Mitra" <[EMAIL PROTECTED]>
Sent: Friday, June 10, 2005 06:41 PM
Subject: RE: Observer-Moment Measure from Universe Measure


>
>
> >-----Original Message-----
> >From: Saibal Mitra [mailto:[EMAIL PROTECTED]
> >Sent: Friday, June 10, 2005 11:39 PM
> >To: Brent Meeker; everything
> >Subject: Re: Observer-Moment Measure from Universe Measure
> >
> >
> >
> >----- Original Message -----
> >From: "Brent Meeker" <[EMAIL PROTECTED]>
> >To: "Saibal Mitra" <[EMAIL PROTECTED]>
> >Sent: Wednesday, June 08, 2005 02:23 PM
> >Subject: RE: Observer-Moment Measure from Universe Measure
> >
> >
> >>
> >>
> >> >-----Original Message-----
> >> >From: Saibal Mitra [mailto:[EMAIL PROTECTED]
> >> >Sent: Wednesday, June 08, 2005 1:16 PM
> >> >To: Patrick Leahy; Hal Finney; [EMAIL PROTECTED]; [EMAIL PROTECTED]
> >> >Cc: everything-list@eskimo.com
> >> >Subject: Re: Observer-Moment Measure from Universe Measure
> >> >
> >> >
> >> >I think one should define an observer moment as the instantaneous
> >> >description of the human brain. I.e. the minimum amount of information
> >you
> >> >need to simulate the brain of a observer. This description changes
over
> >time
> >> >due to interactions with the environment. Even if there were no
> >interactions
> >> >with the environment the description would change, but this change is
> >fixed
> >> >by the original description.
> >>
> >> That means that, supposing the brain is a classical, the "moment"
cannot
> >be
> >> defined by a description of values, omitting rates; just as the path of
a
> >> ballistic projectile cannot be specified by it location, omitting its
> >velocity.
> >> But to include rates means an implicit introduction of time and
continuity
> >of
> >> OMs.  This implies that OMs form causal chains and it makes no sense to
> >talk
> >> about the same OM being in two different chains.
> >
> >
> >That's true in an isolated personal universe that is not interacting with
an
> >'outside world'. I could, e.g. take your brain and simulate that on a
> >computer. The evolution equations for your brain are deterministic, so
the
> >simulation will describe a unique chain of causal links provided you fix
the
> >boundary conditions.
> >
> >If the personal universe is embedded in another universe (like in our
case),
> >then the evolution equations will be constantly perturbed.
> >
> >
> >
> >
> >>
> >> But a lot of the motivation for OMs comes from the brain *not* being
> >classical;
> >> from the idea that the brain gets "copied" into Everett's multiple
> >relative
> >> states or MWIs.  Decoherence in the brain is very much faster than the
> >> neurochemical processes - that's why it's approximately classical.  So
> >what is
> >> going on when QM predicts different OMs?  From Everett's point of view
the
> >> brain must be treated as part of the QM system and it gets "copied" -
but
> >not
> >> by itself.  Its description must include its entanglement with the
quantum
> >> systems observed.  So it seems that in either case, classical or
quantum,
> >an OM
> >> as a description of a brain state, has links outside itself.  In the
> >classical
> >> case it has casual links in time.  In the QM case it has Hilbert space
> >links to
> >> what has been observed.
> >
> >
> >I agree. But the entangled state of a brain with the rest of the universe
in
> >the MWI corresponds to an ensemble of different worlds such that in each
> >member of the ensemble the brain is in some definite state.
> >
> >
> >>
> >> >So, I see no problem with Hal's way of thinking about OMs....
> >> >
> >> >
> >> >Observers are can be thought of as their own descriptions and thus
> >universes
> >> >in their own right. Observer moments are observers in particular
states
> >i.e.
> >> >their ''personal'' universe being in a certain state. The causal
relation
> >> >between successive states is already defined when we specify which
> >observer
> >> >we are talking about. i.e., we have already specified the laws of
physics
> >> >for the personal universe of an observer which defines the observer.
> >> >Specifying the initial state of the personal universes thus suffices.
> >>
> >> That would hold for a classical brain in a classical universe.  But
does
> >it in
> >> a QM universe?  I see a tension between the idea of "personal universe"
> >and
> >> quantum entanglement.
> >
> >I don't see problems here. If you assume that our universe is described
by
> >some fundamental laws of physics then those laws of physics also describe
> >our brains. The way a particular brain works is thus fixed. This then
> >defines the personal universe.
>
> There seems to be a big jump between those last two sentences.  Defining
the
> laws of physics may define the *way* a brain works - but not its content,
not
> the specifics of its processes - and the same for a universe.
>
> >Entanglement of the brain with another system
> >can only happen if there are interactions with the outside.
>
> Sure, and there must be such interactions according to what we know of
physics.
>
> >Even in the
> >classic case these intercations make the evolution of the personal
universe
> >nondeterministic.
>
> Right.  But in that case on "observer moment", defined as: "...one should
> define an observer moment as the instantaneous description of the human
brain.
> I.e. the minimum amount of information you need to simulate the brain of a
> observer." may have to include a lot of the universe outside the brain,
i.e.
> all the part that the brain is entangled with.   And in principle it's
> entangled with all those other MWs.



I disagree here. Even a lot of what is going on inside the brain is not
relevant for consciousness. A well known example is that of people who have
lost their sight due to brain damage. In some cases signals from their eyes
still reach the brain but the part responsible for vision doesn't function
anymore. In some cases these signals allow the person to avoid obstacles,
but the patient experiences such an avoidance movement as an involuntary
movement.


Saibal

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