On 22-04-2018 06:08, Brent Meeker wrote:
On 4/21/2018 8:39 PM, smitra wrote:
On 22-04-2018 02:05, Brent Meeker wrote:
On 4/21/2018 4:45 PM, smitra wrote:
Yes, collapse does imply non-locality, but note that in the MWI
there is no collapse. There is no real "splitting of Worlds" in the
MWI either, it's only an effective splitting that can be interpreted
as an effective collapse as observed in the various effective
worlds.
And that observation is predicted by events spacelike separated from
it.
Brent
And that ability for Alice to predict what Bob will find, poses a
problem for single world collapse theories. Only there does new
information appear after a measurement and that then happens in a
non-local way when making certain measurements on entangled pairs of
particles.
There are only four cases without collapse and in every case Alice can
predict Bob's result. The very fact, which you have brought up, that
any hidden variable theory that explains the results must be non-local
(like Bohmian QM) shows that effect is non-local.
Brent
In case of a collapse theory, the non-local effect is far more
problematic. Alice then finds a result at her place and because there is
no other copy of her who found the other result, new information has
appeared. And that means that Bob's result is now also well defined but
the information about his measurement exists at a space-like separation.
In the MWI Bob may know that Alice has already made her measurement, but
he would also know that Alice exists as a superposition of two copies
who will have found two different results, so there exists no
information about what he is about to find later when he will measure
his spin at the distant location where Alice is as that entire place is
in a superposition.
Saibal
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