RE: Sociological approach

From: Patrick Leahy <jpl.domain.name.hidden>
Date: Tue, 24 May 2005 10:45:51 +0100 (BST)

On Mon, 23 May 2005, Brent Meeker wrote:

>> -----Original Message-----
>> From: Patrick Leahy [mailto:jpl.domain.name.hidden]

<SNIP>
>> NB: I'm in some terminological difficulty because I personally *define*
>> different branches of the wave function by the property of being fully
>> decoherent. Hence reference to "micro-branches" or "micro-histories" for
>> cases where you *can* get interference.
>>
>> Paddy Leahy
>
> But in QM different branches are never "fully decoherent". The off axis terms
> of the density matrix go asymptotically to zero - but they're never exactly
> zero. At least that's standard QM. However, I wonder if there isn't some
> cutoff of probabilities such that below some value they are necessarily,
> exactly zero. This might be related to the Bekenstein bound and the
> holographic principle which at least limits the *accessible* information in
> some systems.

I'm talking about standard QM. You are right that my definition of
macroscopic branches is therefore slightly fuzzy. But then the definition
of any macroscopic object is slightly fuzzy. I don't see any need for a
cutoff probability... the probabilities get so low that they are zero FAPP
(for all practical purposes) pretty fast, where, to repeat, you can take
FAPP zero as meaning an expectation of less than once per age of the
universe.
Received on Tue May 24 2005 - 05:51:07 PDT