Re: [foar] Macroscopic superpositions and pure states in the Everettian Interpretation

[Gary Oberbrunner]

On Sat, Jul 18, 2015 at 6:05 PM, John Clark <johnk...@gmail.com> wrote:

But would it really be legitimate ​to call such laws deterministic? It seems to me that to be deterministic a law must not only say that under condition X Y will always happen but also say that under condition X  Z will NEVER happen; but if Many Worlds is true everything will happen. 

 John K Clark

Only everything physically possible.  Under no circumstances will anything that violates the laws of physics happen (such as an object being transported instantaneously to the other side of the solar system).

And indeed as the ever-perspicacious LizR points out, the SWE is only deterministic when integrated over all results (universes).

--

Gary

[Russell Standish]

On Sun, Jul 19, 2015 at 12:38:31PM -0400, John Clark wrote:
> On Sun, Jul 19, 2015 at 2:57 AM, LizR <liz...@gmail.com> wrote:
>
>
> > ​> ​
> > The lack of a global observer isn't necessarily important
> >
>
> ​If you start saying that from a global viewpoint this and that happens
> then it is important if such a viewpoint does not exist. ​
>
> ​Maybe.​
>
> ​>> ​
> >> ​if everything that can happen does happen that's still a astronomical
> >> number of things and maybe a infinite number of things; deterministic laws
> >> are supposed to impose restrictions on what can happen and that's not much
> >> of a restriction.
> >>
> >
>
> ​> ​
> > No, deterministic laws are supposed to say what happens without invoking
> > any intrinsic randomness.
> >
>
> ​Laws are also supposed to say what doesn't happen, Feynman said "Science
> is imagination in a straitjacket" and by that he meant that a law that says
> anything can happen is almost the same as no law at all. For example, all
> the laws of physics (with the important exception of the second law of
> thermodynamics) can be boiled down to saying that something is conserved,
> something can not be created or destroyed, which as Noether proved is
> equivalent to saying something is symmetrical; but if nothing (or at least
> very little) is conserved then nothing (or at least very little) is
> symmetrical and the fundamental laws of physics are starting to look a bit
> anemic. Maybe.
>

Yes - but that was not what was being claimed when the expression
"global viewpoint" came up. The "global viewpoint" in this context is
that of the Multiverse, or Schoedinger's equation, and it has a very
real conservation law - conservation of information.

I agree that "global viewpoint" (like Tegmark's "bird view") is a
rather loose way of talking, as, of course, no such thing can
literally exist. But one can look behind it to work out what is really meant.

Cheers

--

----------------------------------------------------------------------------
Prof Russell Standish Phone 0425 253119 (mobile)
Principal, High Performance Coders
Visiting Professor of Mathematics hpc...@hpcoders.com.au
University of New South Wales http://www.hpcoders.com.au
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[Brett Hall]

On 19 Jul 2015, at 08:05, John Clark <johnk...@gmail.com> wrote:

On Wed, Jul 15, 2015 at 6:28 PM, Nick Prince <nickmag...@gmail.com> wrote:

 

 

Deutsch says on p269 that a phenomena appears unpredictable to observers for three reasons. First is fundamental randomness which he says is excluded because there are no such variables in real physics. Second is that factors affecting the phenomena, though deterministic are unknown or to complex to account for. Third is that two or more instances of the observer become different - he then says that it makes their outcomes strictly unpredictable despite being described by deterministic laws? 

​But would it really be legitimate ​to call such laws deterministic? It seems to me that to be deterministic a law must not only say that under condition X Y will always happen but also say that under condition X  Z will NEVER happen; but if Many Worlds is true everything will happen. 

Many worlds *determines* what can happen. Like what is physically possible.

It *does* say some things never happen. So, for example, it says you can't find yourself in a physically impossible universe. For example: one that violates the laws of quantum mechanics. So you won't find a stationary isolated atom that keeps on gaining mass, getting heavier and heavier, without limit.

Logically, that's a possible world to be in. But because it violates a few physical laws (eg: conservation of energy) you won't find yourself in such a world.

Brett.

[Stathis Papaioannou]

On Monday, July 20, 2015, John Clark <johnk...@gmail.com> wrote:

On Sun, Jul 19, 2015 at 2:57 AM, LizR <liz...@gmail.com> wrote:

 

​> ​

The lack of a global observer isn't necessarily important

​If you start saying that from a global viewpoint this and that happens then it is important if such a viewpoint does not exist. ​

 

​Maybe.​

​>> ​

​if everything that can happen does happen that's still a astronomical number of things and maybe a infinite number of things; deterministic laws are supposed to impose restrictions on what can happen and that's not much of a restriction.

 

​> ​

No, deterministic laws are supposed to say what happens without invoking any intrinsic randomness.

​Laws are also supposed to say what doesn't happen, Feynman said  "Science is imagination in a straitjacket" and by that he meant that a law that says anything can happen is almost the same as no law at all. For example,  all the laws of physics (with the important exception of the second law of thermodynamics) can be boiled down to saying that something is conserved, something can not be created or destroyed, which as Noether proved is equivalent to saying something is symmetrical; but if nothing (or at least very little) is conserved then nothing (or at least very little) is symmetrical and the fundamental laws of physics are starting to look a bit anemic. Maybe.  

Probabilities are still valid in a deterministic multiverse. You can calculate that if the half life of an atom of a radioisotope is one second, then for all practical purposes it is impossible that you will find yourself in a universe where it hasn't decayed after an hour. This is even though it is a deterministic fact that the atom both decays and does not decay.

--
Stathis Papaioannou