On 06 Feb 2017, at 18:12, Stathis Papaioannou wrote:
On Mon., 6 Feb. 2017 at 11:06 pm, Ronald Held <ronaldh...@gmail.com>
wrote:
Why Boltzmann Brains Are Bad
Authors: Sean M. Carroll
Comments: 27 pages. Invited submission to a volume on Current
Controversies in Philosophy of Science, eds. Shamik Dasgupta and Brad
Weslake
Subjects: High Energy Physics - Theory (hep-th); Cosmology and
Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum
Cosmology (gr-qc); History and Philosophy of Physics (physics.hist-ph)
Some modern cosmological models predict the appearance of Boltzmann
Brains: observers who randomly fluctuate out of a thermal bath rather
than naturally evolving from a low-entropy Big Bang. A theory in which
most observers are of the Boltzmann Brain type is generally thought to
be unacceptable, although opinions differ. I argue that such theories
are indeed unacceptable: the real problem is with fluctuations into
observers who are locally identical to ordinary observers, and their
existence cannot be swept under the rug by a choice of probability
distributions over observers. The issue is not that the existence of
such observers is ruled out by data, but that the theories that
predict them are cognitively unstable: they cannot simultaneously be
true and justifiably believed.
--
Here is the link:
https://arxiv.org/pdf/1702.00850.pdf
Everything I've ever seen written about Boltzmann Brains takes the
position that they are obviously absurd. But here's another view:
Boltzmann Brains would give rise to every possible thought - every
possible observer moment. This is equivalent to the situation
whereby every possible observer moment exists necessarily as a
Platonic entity, without the need for a separate physical universe.
The appearance of a stable physical universe then emerges from the
ensemble of these observer moments.
I do not think anymore that Boltzmann brain are brain or computational
device, nor that the notion is well defined. But a part of Carroll
reasoning could work using the Universal Dovetailing instead, which
are deterministic process and do represent computations (unlike the
Boltzmann brain, which, as far as I can provide sense to them are
analog of the "white rabbits" or even "white noise"). In a physicalist
and non computationalist context, Carroll's conclusion makes some
sense. Yet, with computationalism, it looks like advocating a small
non robust universe, which is move that the step 8 of the UDA shows to
be not working.
Bruno
--
Stathis Papaioannou
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