On 5/13/2015 6:04 PM, LizR wrote:
On 14 May 2015 at 12:32, Russell Standish <li...@hpcoders.com.au
<mailto:li...@hpcoders.com.au>> wrote:
On Thu, May 14, 2015 at 11:26:17AM +1200, LizR wrote:
> On 13 May 2015 at 18:20, Russell Standish <li...@hpcoders.com.au
<mailto:li...@hpcoders.com.au>> wrote:
>
> > For a robust ontology, counterfactuals are physically instantiated,
> > therefore the MGA is invalid.
> >
>
> Can you elaborate on this? ISTM that counterfactuals aren't, and indeed
> can't, be physically instantiated. (Isn't that what being counterfactual
> means?!)
No - counterfactual just means not in this universe. If its not in any
universe, then its not just counterfactual, but actually illogical, or
impossible, or something.
>
> As I mentioned, a simple example is my decision between tea and coffee. In
> the MWI (or an infinite universe) there are separate branches (or
> locations) in which I have both - but in the branch where I had tea, I
> didn't have coffee, and vice versa. And because those branches can't
> communicate, the road not taken remains counterfactual and non-physical
> within each branch. Isn't that enough for the MGA to not need to worry
> about counterfactuals, even in the MWI/Level whatever multiverse?
>
Why is communication needed?
Because otherwise there can be no physical influence, and - within the branch(es) in
which the MGA is being carried out - the recorded system is identical to the
non-recorded one. Without any physical communication / interference there is no
difference from a single universe version. Well, ISTM, at least.
This a point I find confusing. If we're accepting physics as we think it works, then the
reason you don't experience a superposition of drinking tea and drinking coffee is that
there is interference that nulls out the cross terms in the density matrix. So when we
say decoherence has eliminated interference/communication between these two subspaces, we
meant "at a classical level". At the QM level it is the "inteference" of the environment
that makes the subspaces orthogonal.
But if we're not accepting physics, if we're trying to derive physics, as Bruno is, then
we're starting from the classical=TM computation and we have to derive the phenomenon of
quantum interference within the classical computation.
Brent
--
You received this message because you are subscribed to the Google Groups
"Everything List" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to everything-list+unsubscr...@googlegroups.com.
To post to this group, send email to everything-list@googlegroups.com.
Visit this group at http://groups.google.com/group/everything-list.
For more options, visit https://groups.google.com/d/optout.
