On 16 Mar 2017, at 00:41, Brent Meeker wrote:
I think Sabine is wrong when she says that one must use qubits to
compute the universe. Anything computable by a quantum computer is
computable by a classical (Church-Turing) computer, with the penalty
of
an exponential slowup. Sabine makes some good points, one of which
I've
tried to make with Bruno. Bruno (and Tegmark) aren't thinking of a
physical computer (as Sabine apparently is); they're Platonist and
they're thinking of a Turing machine or other abstract "computer" that
computes everything. Bruno likes to cite a set of Diophantine
equations
that constitute a universal computer. But as Sabine observes, the
computation of the universe can't just be a computation of your
thoughts.
There is no computation of the universe. There can be only computation/
emulation of your thought. The physical universe emerge from a NON
COMPUTABLE statistics on all the computation of "my" thought. That is
used in the computationalist non-cloning theorem.
In order that your thoughts be "about" something, the
something must be computed too.
But then we would not been able to dream. In a dream, we are cut from
the environment, and yet have thought about something (usually built
by the neo-cortex from plausible quasi-random data generated by the
cerebral stem, in some theory)
There's no other way to assure that
your thoughts will correspond to a universe.
Which can be a reason to be skeptical about "a universe".
But then we're back to her
first point that of course the universe is computed in this trivial
sense that everything is computed.
With computationalism, only thought are computed, not what the thought
can possibly be about, which emerges from an infinity of computations
(due to the first person inability to compute the result of the self-
multiplication, and to see if there are delays, etc.).
I think Bruno understands and
accepts this point, but he sees his theory that every possible
computation is performed (by a universal dovetailer) and our
multiverse
is just one of the things computed as an explanation that is beyond
trivial.
Tegmark is closer to this, but I criticized him on exactly this. Even
with a very low substitution level, the physical reality remains out
of all possible computations (and that is why we can be very skeptical
that the notion of "physical universe" makes any sense.
He says it implies quantum mechanics via the
first-person-indeterminancy principle. I think that's still trivial.
It is simple, but not trivial, as you can see how strong gnostic
atheist still get stuck on the first person indeterminacy. Moreover,
the math of the first person indeterminacy, needed to get physics is
highly not trivial, as it is based on Solovay theorem, itself based on
Gödel and Löb, the universal machine (a highly non trivial notion as
it requires closure of a set of functions for the diagonalization,
etc.).
The illusion/appearances of the universe is a very non trivial
arithmetical phenomenon. Without Gödel's incompleteness, there is no
phenomena at all in arithmetic!
Bruno
Brent
On 3/15/2017 2:57 PM, Bruce Kellett wrote:
Sabine Hossenfelder has an interesting blog post about the popular
idea that we are living in a simulation created by some
super-intelligence somewhere. She is not impressed with the idea....
http://backreaction.blogspot.com/2017/03/
I think she makes some good points. Maybe Wolfram and Bruno should
listen in....
Bruce
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