On Wednesday, August 21, 2019 at 3:13:11 PM UTC-6, Lawrence Crowell wrote: > > On Tuesday, August 20, 2019 at 4:56:23 PM UTC-5, Alan Grayson wrote: >> >> https://en.wikipedia.org/wiki/Conformal_cyclic_cosmology >> >> Is this a viable theory for avoiding a BB interpreted as a singularity? AG >> > > Penrose proposed a conformal identification of spatial infinity in the > past and future i^±∞ of FLRW spacetimes. A cosmology expands and in the > limit time → ∞ it transitions into a new cosmology. The de Sitter vacuum is > not eternally stable, so the idea may have some germ of relevancy. I am not > sure about how this would work with vacuum to vacuum transitions. The > exponential expansion of the universe is a sort of time dependent conformal > transformation with a small vacuum expectation for the scale field. To > transition to a new cosmology, say with inflationary expansion, this means > the vacuum expectation is increased. > > The overall physics community response to this has been tepid at best. > There are some possible conflicts with observed data. > > LC >
FWIW, ISTM that what GR might be indicating about the BB, is that, insofar as it's a singularity, it couldn't have occurred, and didn't occur. This is to say the universe didn't become infinitely small in spatial extent, like a mathematical point, but rather that there was a maximal finite value of its energy density, hugely high but not infinite. For this reason I find the cyclic models promising, although, as you rightly indicate, they're far from complete or bug-free. AG -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/82af5542-50b2-4bd1-b0ad-be923cd3f242%40googlegroups.com.
