- #1
wabbit
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Reading
http://www.aei.mpg.de/~rezzolla/lnotes/mondragone/collapse.pdf
If so, assuming R0 is (significantly) larger than the radius of the observable universe, are there in principle observational differences between this (a variant of the interior of a white hole or time-reversed black hole) and our expanding universe?
Of course this would violate the cosmological principle since it would, in this simple case, imply a homogeneous distribution out to a certain radius and nothing after that - but other than that, is there a way to distinguish the two?
http://www.aei.mpg.de/~rezzolla/lnotes/mondragone/collapse.pdf
The reasonning looks like it should generalize from pressureless dust to a matter-radiation mix, and presumably also works with a (small) cosmological constant thrown in, as in a Schwarzschild-de Sitter solution - is that a correct assumption?(p. 19) In spherical symmetry, the dynamical spacetime of a collapsing (expanding) region occupied by homogeneous matter is a Friedmann-Robertson-Walker (FRW)-Universe (...)
There is an important difference between the FRW Universe and the spacetime of an OS collapse since in the latter case not all of the spacetime is occupied by matter (the dust sphere has initially a finite radial size R0) and the vacuum portion (i.e. for R > R0) will be described by a Schwarzschild spacetime.
If so, assuming R0 is (significantly) larger than the radius of the observable universe, are there in principle observational differences between this (a variant of the interior of a white hole or time-reversed black hole) and our expanding universe?
Of course this would violate the cosmological principle since it would, in this simple case, imply a homogeneous distribution out to a certain radius and nothing after that - but other than that, is there a way to distinguish the two?