Re: ASSA and Many-Worlds

From: Brent Meeker <meekerdb.domain.name.hidden>
Date: Sun, 28 Jan 2007 11:47:27 -0800

Jason Resch wrote:
> On 1/28/07, *Stathis Papaioannou* <stathispapaioannou.domain.name.hidden
> <mailto:stathispapaioannou.domain.name.hidden>> wrote:
>
>
> Consciousness *seems* to be continuous even if at a fundamental level
> time or brain processes are discrete. Also, although I agree that
> there is no necessary connection between observer moments, there
> *seems* to be a connection, in that almost by definition I won't
> suddenly find myself turning Chinese in the next moment even though
> there are 50 times as many Chinese as Australians in the world. If
> the feeling that I remain the same person from moment to moment is an
> illusion, then I am interested in how that illusion can be
> maintained, regardless of the underlying mechanisms of consciousness,
> time, whether or not there exists a real world, and so on.
>
>
>
> I think the reason the illusion is maintained is rather trivial,
> whenever your brain has the thought: "How come I was born as Stathis
> Papaioannou, and only ever remember being Stathis Papaioannou?" Your
> brain is limited to the memories contained within it. And since
> there is no way for your brain to have integrated memories of what it
> is like to be other observers, your illusion of personal identity is
> maintained.
>
>
>
>
> Either I'm one of few or one of many. If everyone guesses that they
> are one of many, more are going to be right than if everyone guesses
> that they are one of few. Therefore, I should guess that I'm one of
> many. Is that what you are suggesting?
>
>
> Yes, and once we assume we are probably one of many similar or
> identical observer-moments, we should ask "Why should there be many?"
>
>
>
> The argument has some appeal assuming we have no other reason to
> favour guessing that we are one of many or one of few. However, lack
> of evidence against something does not necessarily mean that thing is
> likely or even possible. As it happens there is perhaps some evidence
> for MW from quantum mechanics, but were it not for this, we could
> easily class MW along with pink elephants as something very unlikely
> which cannot be rescued by the ASSA.
>
>
> If many-worlds is true, consider for a second how many histories
> lines (and copies of you) must have been created by now. The
> universe had been branching into untold numbers of copies, untold
> numbers of times each second, for billions of years before you were
> born. While not every branch contains you, once you appeared in one
> history line, a new copy of you has been created for every possible
> outcome of every quantum event that happens anywhere in this
> universe.

I don't think this is the way to look at it. It's true that QM predicts an uncountably infinite number of branchings, even for an universe containing only a single unstable particle. But these branchings don't produce different copies of Stathis. As a big macroscopic object he is described by a reduced density matrix that has only extremely tiny off-diagonal terms. So he is a stable entity against these microscopic quantum events unless they are amplified so as to change his macroscopic state - as for example if he heard a geiger counter click. The microscopic events just add a little fuzz to his reduced density matrix - and the same for all of the classical world.

You might be interested in Greg Egan's excellent SF story "Singleton" which is available online:

ttp://gregegan.customer.netspace.net.au/MISC/SINGLETON/Singleton.html

Egan says "People who professed belief in the MWI never seemed to want to take it seriously, let alone personally." So he wrote a story in which it is taken personally.

Brent Meeker

>I would be astonished if many-worlds turned out to be
> false, not only because of ASSA, but also due to due to the paradoxes
> that exist in other interpretations, and David Deutsch's reasoning
> that the computations of a quantum computer must be done somewhere,
> and single-world views cannot explain, for example, how Shor's
> algorithm works.



>
> From a mathematical/computational perspective a many-world universe
> has only marginally more complicated description (program) than a
> universe that has a one-to-one mapping of states.
>
> For a simple example of how this is possible, consider the Fibonacci
> sequence, defined as: F(0) = 1 F(1) = 1 F(n>1) = F(n-1) + F(n-2)
>
> But a sequence that defines an exponentially growing number of states
> can be made just by changing the + to a plus or minus: F(0) = 1 F(1)
> = 1 F(n>1) = F(n-1) ± F(n-2)
>
> Therefore mathematical descriptions of universes like our own should
> be common, and only slightly rarer than universes that lack the
> property of many-worlds. However, many-worlds universes define so
> many more states, and so many more observers that most of reality
> should be generated by short programs that define massive numbers of
> states before halting. An interesting question: What about programs
> that loop, would observers and states in such a universe have an
> infinite measure or should looping be treated the same as halting?
>
> Jason
>
>
> >


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Received on Sun Jan 28 2007 - 14:47:43 PST

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