The observer is both inside and outside the system. There is a potential self interaction within the observer, which is mind (non-colloquial mind; mind represents awareness and interaction), and is why we see two different modes of reality in observation and “non-observed” observation aka the wave particle duality of the double slit.
Interested layperson here...I have a question....Following the reasoning Susskind presents in this lecture, is the GHZ Brane then analogous to the node between the two " boxes" in the double slit/wormhole idea?
the split of world at each observation is totally unnecessary consequence of Everett’s relative state. The wave-function of observer is a way more economical way then wave-function of “entire” universe since observer's observations are the only & only what effectively exists and accessible for observer to test, the only observer's state is available for observer to test/run any experiments. Thus, it makes no sense to talk about wave function of universe since universe is an emergent phenomenon derived from observer's states thus “entire universe” is an observer’s assumption to comply with observer believe for objectivity of reality. Such quantum system as an observer is a way less complex quantum system as entire universe. In some extent both can be considered as an approximate invariant. "entire universe" version assumes existence of objective reality while "observer version" makes no assumption about that at all.
@Breadstick Shrimpfry >" to observer independent phenomena at all" --- EXACTLY!!!! it's the point, there is no way to have an observer independent phenomena at all. Once you start to talk about "independent" you do make an assumption about "objective reality", it's not necessary to make, math works fine without such assumption. It does not preclude to believe in "objective reality" just do not add it to the math framework. Since only & only accessible information is the state of observer thus, Everett's "universal wavefunction" is in fact the "observer wave function".
All I see is that engineers have a program to satisfy triangles and as long as you don’t throw your dice on a straight line you are good to go with a computer
You are correct but overthinking. A wave function is a property of the quantum mechanical ensemble. There can be no ensemble of universes. The universe is, by definition, a singleton. ;-)
