Comments on Soul Physics: Penrose in Pittsburgh

As I recall, it's the "rescaling" across the confo...

2010-06-08T08:18:16.196-04:00

As I recall, it's the "rescaling" across the conformal boundary that does the trick.

At the "end" of an aeon, the cold massive particles meet their demise. But the massless particles can be thought of as continuing to the conformal boundary at t=infinity -- after all, massless particles don't have proper time. So, an aeon ends with an initial spacelike conformal surface, with massless particles on it.

At the "beginning" of an aeon, as you get very close to the big bang, temperatures get so hot that all particles become massless. So again, you get a bunch of massless particles on a conformal surface.

Penrose's trick is to identify these two conformal surfaces. But conformal surfaces (and, as far as we can tell, massless particles) are conformally invariant. So any notion of "scale" is lost as we cross the conformal boundary -- what were cold, far-apart particles can become hot, close-together particles in a new aeon, depending on how the metrics of the individual-aeons are related.

If the universe expand so much at the end of a giv...

2010-06-08T04:34:19.544-04:00

If the universe expand so much at the end of a given aeoan, so that it gets so cold to the point that even black hole is too hot and has to radiate all its mass outward. Then how is the universe supposed to get colder still to precipitate new matter once it pass through to a new aeoan?

Yep! But at the same time, I don't think his cons...

2009-06-28T14:38:54.246-04:00

Yep! But at the same time, I don't think his construction requires 'aeons all the way down' -- you could just as easily paste together only two aeons.

A finite-aeon cosmology does seem more physically palatable. Unfortunately, I don't think it would solve all the philosophical problems that Penrose is targeting: there would be no explanation of black-hole evaporation in the "latest" aeon, and no explanation of early-Universe low entropy in the "earliest" aeon.

So instead of 'turtles all the way down' it is 'ae...

2009-06-28T14:04:09.849-04:00

So instead of 'turtles all the way down' it is 'aeons all the way down' ?
Does he actually suggest an infinite number of them?

Update: There is a PDF sketching Penrose's idea in...

2009-06-18T16:52:16.485-04:00

Update: There is a PDF sketching Penrose's idea in the EPAC 2006 Proceedings. Unfortunately, I haven't yet found anything newer in writing.