Graduate Consistency/continuity in the MWI

[jms5631]

Hello, and thank you for any input. This forum is a wonderful venue for gathering information and clarity on otherwise quite abstruse topics. I have had an enduring interest in QM interpretations for some time(and quantum mechanics generally), and find their diverse ontological and epistemological implications intriguing.

One thing, however that I can't seem to grasp no matter how hard I try to conceptualize(and this is surely a limit on myself rather the interpretive framework itself) is how continuity or consistency is attained in the Many Worlds Interpretation. In this vast sprawling network of continuous branching, how do we have a sense of macroscopic agreement, and persistence of identity over time?

How do we agree on events that occurred 30 days or 30 years ago remain enduring facts of our universal history over time? Is information about the smallest minutia of events stored in our branch history that we are consistent with? Essentially, how does the MWI ensure the consistency of observers and systems over time in the midst of this splitting process?

Thank you again for any and all input, and apologies if my question lacks technical rigor.

 

[PeterDonis]

In this vast sprawling network of continuous branching, how do we have a sense of macroscopic agreement, and persistence of identity over time?

Because in each branch of the MWI, once something has happened, it stays happened. Every future event in all the branches that split from a particular branch must be consistent with the past that was observed in that branch. All of the different, inconsistent results of particular events are in different branches that can never make contact with each other again, so the fact that they are different doesn't matter.

 

[jms5631]

Thank you for your reply. I assumed MWI must have strong consistency requirements, but it is certainly a difficult thing to comprehend intuitively-as is much of quantum mechanics. So is it fair to stipulate the following: In any branch(or world) at any time, there is consistency/agreement among all systems or observers(at least in principle) regarding the past and present events. Disjoint events are strictly separated from each other at any point on the worldline, and alternative timelines are all fully consistent at every point in time. Thank you again sincerely for helping clarify this framework for me.

 

[PeterDonis]

In any branch(or world) at any time, there is consistency/agreement among all systems or observers(at least in principle) regarding the past and present events.

Yes.

Disjoint events are strictly separated from each other

In the sense of being in different branches, yes.