# Re: Tegmark's New Book

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On 09 Jan 2014, at 16:30, Alberto G. Corona wrote:```
```
```
```But the UD argument predict that all the possible universes with all
possible laws will be produced.
```
```

Where?

```
```What is what makes our physical laws
"unique determined" by COMP?'
```
```
That happens already at the step seven.

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I assume there that you, here and now, live in a physical universe which run a universal dovetailer, without ever stopping.
```
```
Assuming comp, how do you predict "exactly", after step six, the experience of dropping a pen in the air?
```What is the probability that you will see falling on the ground?

```
You believe (because you assume comp and agreed up to step 6) that your next immediate future first person state is determined by the FPI on all the emulations of your actual states appearing in the UD* (the complete execution of the UD). This involves infinitely many computations (that should be an easy exercise in computer science: all functions are implemented by infinitely many programs). To compute the exact probability of the event "the "pen fall on the ground", you must seek the ratio or proportion of all computation going through your states where you see the pen falling on the grounds, among all computations going through your states.
```
```
Computations is an arithmetical notion, and your actual state is given by a relative number, encode locally by the doctor. The entire UD is itself definable in arithmetic. So, in that step seven, if comp is correct or believed by a rational agent, the rational agent had to believe that physics, all physical predictions, is reduced to one "simple law": basically a measure on the relative computations. Physics has been reduced, in principle (of course) to a statistical sum on all first person valid relative computations.
```
```
Below our substitution level, physics is not given by "one computation" (or one universal numbers). Physics is given by an infinity made of almost all computations. It involves a competition among all universal numbers. "Almost all" means all those validating your first person experience. Then the math shows that the case of "probability one", for that statistics on first person valid computations obeys a quantum logic.
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In fact comp gives a criteria to distinguish geography (which depends on many indexicals) and physics, which appears to be indexical independent. Physics is even independent of the choice of the base of the phi_i.
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There is no "real" (ontic) physical reality, but still a *unique* (yet relative, conditional) measure on consistent enumerable extensions on all computations (going through your current states). (Unless comp is false or that we are manipulated through a normal simulation). Physics is transformed into the study of a lawful precise arithmetical phenomenon of a type "first person plural experience".
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You have to understand all this by yourself. Reread with attention and concentration all UDA steps, as they are all used at once in the step seven.
```
Bruno

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2014/1/9, Bruno Marchal <marc...@ulb.ac.be>:
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```
On 09 Jan 2014, at 12:23, Alberto G. Corona wrote:

```
```"But with comp the laws of physics are uniquely determined by a
statistical sum on an infinity of computations"

Uniquely determined?  That is like saying that The Buckingham Palace
```
is uniquely determined by the statistical sum of a infinity of pieces
```of lego thrown in the site by infinite B52 bombers.
```
```
You might confuse geography and physics. The (sigma_1) arithmetic is
the same for all, and the laws of physics must be given by the same
laws for any universal machine. Comp makes physics invariant for all
machine-observers, and entirely determined by the unique measure on
all computation, as seen from the 1p view. This should be clear from
the UD-Argument. Comp makes the primitive universe into a fairy tle,
but by doing so, it makes the physics much more solid (indeed physics
is deduced from addition and multiplication only, with comp at the
meta-level).

Bruno

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```
2014/1/9, Bruno Marchal <marc...@ulb.ac.be>:
```
```
On 08 Jan 2014, at 23:53, LizR wrote:

```
```On 9 January 2014 11:40, meekerdb <meeke...@verizon.net> wrote:
On 1/7/2014 10:36 PM, LizR wrote:
```
Max's main lacuna is the nature of consciousness, which he describes
```as "what data feels like when it's being processed" - hardly a
```
detailed theory. He starts his Mathematical Universe Hypothesis from
```the opposite pole to Bruno, so to speak. I wonder if it's possible
for a particular mathemathical object to drop out of comp - after
```
all, we do appear to live in a universe with a specific set of laws of physics. Are these the only ones that could be generated by comp
```(or generated by the existence of conscious beings in Platonia) ?
Maybe one needs to somehow intersect comp with the MUH to get the
full story!

```
I think to be conscious you need memory and a sense of time passage
```(although Bruno disputes this when he comes back from a salvia
```
trip). To escape solipism there must be objects your perceive, some
```of which act like you, and on which you can act (c.f. Dr Johnson).
```
That implies that there must be a quasi-classical world in order to
```support consciousness (at least human-like consciousness).

Those all seem like reasonable criteria. I imagine they could be
fulfilled by a variety of physical laws (e.g. it probably wouldn't
make a huge difference to the existence of human beings if light
travelled 10% faster or slower). So presumably comp covers all
possible physical laws which create conscious beings...
```
```

But with comp the laws of physics are uniquely determined by a
```
statistical sum on an infinity of computations, and is unique (modulo
```that multiplication by three, as physics appears in three
hypostases).
And the determination is based on the FPI, and so physics is NOT a
```
priori Turing emulable. The evidence that physics seems computable is
```a problem for comp, not an evidence for it. Fortunately the
*apparent*
"collapse" might be non-computable enough for comp to be correct.

Bruno

http://iridia.ulb.ac.be/~marchal/

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