On 31 Jul 2012, at 17:36, smi...@zonnet.nl wrote:

Citeren Bruno Marchal <marc...@ulb.ac.be>:

On 30 Jul 2012, at 19:57, meekerdb wrote:

On 7/30/2012 2:19 AM, Alberto G. Corona wrote:
The Boltzman brains , according with what i have read, are completely different beasts. Boltzman pressuposes, that , since no random arrangement of matter is statistically impossible, and Boltzman demonstrated it in certain conditions (ergodic conditions) , with enough time, some arrangements of matter would simulate minds, or even worlds and civilizations. But 15.000 Million years, that is the age of the universe is not enough.

Boltzman was considering the question of how the universe came to be in its state of low entropy. I could be due to a random fluctuation. And it was more probable that the random fluctuation simply produced the universe as we see than a fluctuation that produced a big bang universe which then evolved into what we see.

Actually I doubt this, like the probability that life appears on earth and leads to us, is plausibly bigger than the probability that "I" appears here just now, in my exact current state.

And extending this line of thought further, a fluctuation that merely created a brain along with the illusion of this universe was still more probable (i.e. less improbable).

If that were true, that could be used to put more doubt on the existence of the 1-person indeterminacy measure, I think.

In the UD, or arithmetic, this reflects the competition between little numbers (simple explanation) and big numbers (algorithmically complex explanation). But the indeterminacy bears on all numbers, so the little one have to multiply much more than the complex one, in some ways. Linearity at the physical bottom might be explained by that phenomenon, qualitatively.

Sean Carroll has a good discussion of this and why this argument does not hold for a multiverse, in his book "From Infinity to Here".

Looks interesting. I guess this can be very easily extended to the "many dreams" occurring in arithmetic.



The problem is to explain also why the entropy of the early universe was so low. If you just accept that this is the case and also don't bother about the very distant future, there is no problem. But if you assume that time goes on from the infinite distant past and/or to the infinite distant future, you have a problem, because smaller local low entropy states are then more likely than the whole observable universe being in some low entropy state.

And Sean Carroll's argument amounts to simply hiding the problem in an ever expanding state space, it's not that he has shown that in a multiverse the problem doesn't occur.

But with comp I don't see how we could avoid the ever expanding state space. That is what a UD is, notably, and its existence is a consequence of simple laws (+ and *). Should not a quantum multiverse also contains some quantum universal dovetailer and avoids the problem in the Sean Carroll way? (as far as I can imagine it)



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