# Many-Worlds, Inflation & Dark Energy

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1. Sep 15, 2014

### tionis

Are there any predictions made by the Many-Worlds interpretation of QM that could be ascribed to inflation and or dark energy? In other words, could the hypothetical branching cause our universe to expand?

2. Sep 15, 2014

### phinds

MWI does not make ANY testable predictions. There are proponents of the MWI that wish very much that it DID so that they could show that it's real, but there are others who doubt it actually describes any reality. As long as there are no testable predictions, it's going to be impossible to tell one way or the other.

3. Sep 15, 2014

### The_Duck

All interpretations of quantum mechanics make the same predictions. That is why we call them interpretations, and not theories.

4. Sep 15, 2014

### tionis

OK. What I'm asking is: do these ''branchings'' occur continuously and smooth or are they quantized (i.e. a branching cannot occur until certain energy conditions are met)?

5. Sep 15, 2014

### bhobba

We don't really know.

The continuous formulation of QM via Rigged Hilbert Spaces (it's the correct formulation - the Hilbert Space formulation has issues with stuff like Dirac Delta Functions etc that's used in practice) has unphysical things like solutions that are not zero at infinity. Are these simply things introduced for mathematical convenience (that's my view) or is it trying to tell us something deeper touching on the outcomes of observations are fundamentally discreet in some way.

Thanks
Bill

6. Sep 15, 2014

### tionis

Thanks, bhobba. You said ''we don't know,'' but do we know if inflation or the exponential expansion of the universe (dark energy) have an analog value corresponding to any quantum phenomena associated with the MWI? For example: a certain numerical value of such and such MWI action (unknown to me, obviously lol) is similar to the value of this (insert value here) inflationary or dark energy process? In other words, is there a logical place in the MWI to assume that the inflation/now expanding accelerating phase of the universe comes in quantized chunks? Make sense?

7. Sep 15, 2014

### bhobba

Right now we do not know the origins of dark matter/energy. Things will probably be clearer in say 10 years time - but right now we do not know.

I think it can safely be said its got nothing to do with the MWI. Note the word - interpretation - in MWI - that means its indistinguishable from the QM formalism - and for good reason - it was deliberately cooked up to be so.

Thanks
Bill

8. Sep 16, 2014

### tionis

It seems I don't understand MWI. I thought the interpretation expanded QM with its own mathematical formalism and stuff. And that perhaps hidden in it were some potential answers to modern cosmological conundrums. Oh well, lol.

9. Sep 16, 2014

### stevendaryl

Staff Emeritus
Bill, maybe you know the answer to a mathematical question that I hope isn't too off-topic.

In the usual way of doing quantum mechanics, it seems that the assumption is that the universe is either finite or "asymptotically empty" (meaning that the probability of finding a particle at location $x$ goes to zero as $x \rightarrow \infty$). QFT has a similar assumption of "asymptotic emptiness" in that it (or at least in the development that I've seen) assumes that the Hilbert space is a disjoint union of spaces with a finite number of particles (Fock space).

However, if the universe is infinite (which I think is consistent with what we know about it), then it seems that there should be an infinite amount of matter, and an infinite number of particles. There would still be a finite number of particles in any galaxy, but there would be infinitely many galaxies. Is there a formulation of QM that does not assume that the universe is asymptotically empty? That doesn't assume that the state of the universe is a superposition of states with finitely many particles? In a practical sense, I guess it doesn't matter, because you can view an infinite universe as some kind of limit of finite universes.

10. Sep 16, 2014

### bhobba

I think that QM is a model that ignores such questions. Many assumptions, such as things that don't go to zero at infinity, are simply done for mathematical convenience - blow how reasonable it is.

Thanks
Bill