Re: The scope of physical law and its relationship to the substitution level

[Bruce Kellett]

Pierz wrote:
On Monday, May 25, 2015 at 4:10:37 AM UTC+10, Bruno Marchal wrote:
    On 23 May 2015, at 12:36, LizR wrote:
    I'm not sure why comp would predict that physical laws are
    invariant for all observers

    I can see that it would lead to a sort of
    super-anthropic-selection effect, but surely all possible
    observers should exist somewhere in arithmetic, including ones who
    observe different physics (that is compatible with their existence) ?

    Those with different physics will have measure zero. Why? Because
    the laws of physics must be given by the sum on all computations
    below the substitution level, whatever any universal machine state
    can be in. Only geography will need the anthropic element, the
    physics needs only a mathematical statistics on all computation,
    going in "actual state" which are any state.

    Physics become a theorem of machine theology, itself a theorem of
    arithmetic (+ comp). 

    Of course, today, we don't know how much the "standard model" is
    contingent or absolute. String theory diminish a large part of the
    contingent parts, but introduces complexity in other direction, with
    panorama of different sorts of physics. All this are open problem in
    comp.
    The goal of comp is to provide an explanation of the relation
    between consciousness/mind and appearance of matter and persistence,
    and this in some testable way. It is an explanation in the form of
    the formulation of a problem, or a reduction of a problem into
    another one. 

    Bruno

OK the 'invariant physics' you refer to is a very low-level one, i.e., 
the ultimate unifying laws. However, let me try to put my point about 
the substitution level another way to make it clearer. ISTM that it will 
be sufficient for there to be another region of the multiverse where the 
observable, everyday physics (things like particle masses etc) are 
different in order to force us to conclude that the substitution level 
must be as large as the observer's universe. Why? Because let's say 
there is an observer in another region of the multiverse whom I wish to 
duplicate here in *this* region, where the observable laws are 
different. I get a copy of that observer's memories etc and reproduce 
them here. Now suddenly that observer has a continuation that 
experiences the physics of *this* region. But if that was possible, then 
the physics of both regions would have merged, because observers in both 
regions would already be able to interfere with one another's measures. 
SO, in order to prevent such interference of measures and a merging of 
physics into an average measure, it must be that in order to duplicate 
an observer in another region, I need to duplicate the observer to such 
a deep level that the separation into the two regions is as it were 
enforced by the very definition of that observer. The observer must 
include the entire computational branch down to the point at which the 
two physics diverged.

I think you are largely right here. There is not even any reason to 
suppose that there is an 'invariant physics', even at the lowest of 
levels. If string theory is any guide, then laws such as 
electromagnetism, gravity, the weak and strong nuclear forces, and so 
on, depend on the topological windings of the Calabi-Yau manifolds that 
govern the compactification of the unobserved extra dimensions. Even the 
number of space-time dimensions might vary between these possibilities. 
With even slight modifications of the configurations that obtain in our 
universe, the physics would be very different, and there might well not 
be any 'invariant laws' at all.

So I think you are probably right -- the substitution level must include 
the whole of the level I multiverse (the multiverse over which the same 
laws as we observe obtain). This, at least, will give a block universe 
from which sensible space and time parameters could be extracted. But 
how this is related to the comp summation over multiple instances of an 
individual's conscious moments escapes me completely.

Bruce

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