On 12/4/2017 4:53 PM, Russell Standish wrote:
On Tue, Dec 05, 2017 at 11:26:53AM +1100, Bruce Kellett wrote:
On 5/12/2017 3:15 am, Bruno Marchal wrote:
I think that is enough to get the macroscopic superposition, as, like I
explained, you have to take into account not just the quantum
indeterminacy, + the classical chaos. You might need to shake for some
minutes.
You could shake for longer than the age of the universe and you will still
not convert quantum uncertainties and classical thermal motions into a
macroscopic superposition. Do you know nothing about coherence? And the fact
that coherent phases between the components are what separates a
superposition from a mixture? Random quantum uncertainties and thermal
motions are not coherent, so cannot form superpositions.
To repeat - coherence and superposition are orthogonal concepts.
?? The sum of two solutions to the SE is a solution. It's a coherent
superposition. Nothing orthogonal about it.
A
fully decohered multiverse is still in a superposition.
It is generally assumed that the world is described by a pure state in
Hilbert space. So every branch of the MWI is decohered, but that is
only a loss of coherence FAPP. The branches are still superpositions,
but the cross terms are FAPP small (in the semi-classical basis) and
unknowable, so we trace over them and change the superposition to a
mixture in our representation.
Brent
Re the length of time for quantum uncertainty to affect macroscopic
state, much less than the age of the universe is required.
Whilst the StosszahlAnsatz will be strictly speaking incorrect, as I
understand it it is very approximately true. This will entail that quantum
randomness will affect classical randomness on about the same
timescale as the mean free time of molecules in a gas at room
temperature, or about 0.1 ns.
Unless you are proposing some other source of randomness that is not
quantum? Then I'm all ears. Classical physics doesn't have it, it is
deterministic.
BTW - as Brent pointed out, coin tosses many not actually be a good
example of chaotic inflation of quantum uncertainty, and aren't
actually a good source of randomness - fine, but clearly such systems
do exist, eg lava lamps.
Cheers
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