Peter Soderqvist

TO JESSE

Soderqvist1: According to MWI, from Big Bang and forwardly, when a new branching universe is budding off, aren't these universes in a coherent superposition of states in the moment of budding? And decoherence of superposition of states is factual only afterward? The cat is in a coherent quantum mixture of both dead/alive thus undisturbed in the box, and our measurement (looking in the box) disturb the superposition, therefore the cat splits, or decoherence into one dead, and one alive cat, with one of these cats in our universe, and the other in a another universe?

Peter Soderqvist

I have read in David Deutsch book, The Fabric of Reality, something like this; How can I be in a superposition of states in the moment of budding without knowing anything about it? We don't feel the earth moving either, yet it moves!

Jesse

No, thermal interactions with the external environment are enough to cause decoherence long before we look in the box. It's similar to using electrons vs. photons in the double-slit experiment--photons interact very weakly with the air, so unless we measure which slit the photon went through, we'll get interference on the screen. But electrons interact more with the air, so the only way to get interference with electrons in the double-slit experiment is to perform it in a vacuum--otherwise the air molecules effectively "measure" which slit the electron went through, even if we are never able to reconstruct that information.

Peter Soderqvist

TO JESSE

Soderqvist1: What is so special with external temperature?
The cat is a heat engine too! According to MWI, when an electron is faced with the two holes experiment, the indeterminacy in the electrons "decision" about which hole it will go through? Makes it bud a new universe, and so restore determinism, say; by letting one electron pass through the left hole, and the new one through the right hole. When the universe budding a new one because of that, every sun in the universe does the same! Why is the electron so sensitive to heat, when the rest of the universe can sustain it, namely, both the old, and the new universe are heat systems, which interact in the moment of budding, how can it be so, if heat decoherence the superposition of states?

RoddyM

I agree with Hawking (in this case). We don't need or want Scrodingers cat as a thought experiment.

All we need is Young's experiment. It nails the mystery. Still remains a mystery of course.

Nowhere357

It seems to me that all the indeterminate activity occurs at a level where it "doesn't matter" () until it begans to interact with the determinate world, and then it straightens itself out.

I guess I see no reason that this mystery indicates a "paralell universes" theory. The subatomic particle does exist in two places at once, like harmonic nodes, until it 'solidifies'. There is action at a distance going on, although it's of a strange sort and can't be used to transfer information?

Peter Soderqvist

Where do you draw the borderline between the indeterminate and determinate world? Why just precisely there, and not more upward or downward? What exactly creates this borderline?

Nowhere357

I think all observed borders/boundaries are products of the mind. The border between indeterminate and determinate happen where they interact. Light is partially determinate and partially indeterminate and floods the universe, sort of binding reality together. Feel the force, Luke.

Consider the double slit experiment. The photon is indeterminate until the macro world detects it - until reality insists that the photon 'make up it's mind'. Sort of like, a ball doesn't bounce UNTIL it hits a surface.

This makes more sense to me than a virtual infinity of universes branching off every moment, and a virtual infinity of moments between any two moments.

Every branch creates a whole universe full off matter. Where does all that matter continually come from? I think Occam lops the whole mess off, and we're back to good old UNIverse.

Jesse

Peter Soderqvist
Soderqvist1: What is so special with external temperature?
The cat is a heat engine too!

Sure, but the important question is whether there are any interactions between the cat and the external environment which convey information about the cat's state. If the cat could be completely isolated, it could be as hot as you like, but external systems would receive no information about its state. I haven't studied decoherence in detail so I can't tell you much more about how it works.

According to MWI, when an electron is faced with the two holes experiment, the indeterminacy in the electrons "decision" about which hole it will go through? Makes it bud a new universe, and so restore determinism, say; by letting one electron pass through the left hole, and the new one through the right hole. When the universe budding a new one because of that, every sun in the universe does the same!

Budding a new universe? That isn't really how the MWI interpretation works--after all, if they "budded off" and became totally separate universes, there'd be no interaction between worlds, and thus no interaction between the electron and its counterparts in "other worlds" which is supposed to be the explanation for interference in the MWI. The MWI actually just says there's a single wavefunction for the entire universe which never collapses...the meaning of the "worlds" within this universal wavefunction is a bit fuzzy, and different MWI advocates seem to have slightly different interpretations. See this FAQ:

http://www.hedweb.com/everett/everett.htm

This page also has a good discussion of all the variants of the many-worlds interpretation, which have different ideas about how to defined "worlds" within the universal wavefunction:

http://plato.stanford.edu/entries/qm-everett/

Why is the electron so sensitive to heat, when the rest of the universe can sustain it, namely, both the old, and the new universe are heat systems, which interact in the moment of budding, how can it be so, if heat decoherence the superposition of states?

I don't really know what you mean when you say the universes "interact in the moment of budding"--again, I think you're taking too literal a view of the "worlds" in the many-worlds interpretation. Heat interactions are only important in the sense that they are a form of interaction between the sytem and other systems external to it, and may convey information about the system's state to the other systems.