Sunday, October 23, 2011

The Eternally Existing, Self-Reproducing, Frequently Puzzling Inflationary Universe

The Eternally Existing, Self-Reproducing, Frequently Puzzling Inflationary Universe

Since I cannot comment at Sean's Blog either,  I might as well comment here too:)

27.   Moshe Says:
Igor, I am not sure I understand. We have an initial value problem, so today’s observations are determined once you specify an initial state at some time in the distant past. If you specify the time to be the beginning of the big bang evolution, with the correct but very contrived initial state (nearly homogeneous with just the right kind of fluctuations) then you get no conflict with observation. By contruction, same applies to inflation, because it reproduces that initial state and all subsequent evolution. The only point of inflation is to make that initial state the outcome of prior evolution. By construction all current observations will then be identical, but the initial state will be more natural and less contrived. As I understand Sean’s statement, quantifying this intuitive notion of naturalness is tricky, and it is not always clear inflation indeed comes ahead. I hope I am not mangling things…
And, for the record, in my mind the notion of “naturalness” is one instance of “algorithmic compression”, which is the whole point of seeking a scientific explanation. Without invoking such criteria, by definition (for example) the particle data group review book would be always the best “theory” of particle physics, and you’d never need to learn about gauge theories and spontaneous symmetry breaking and all that stuff.

See Also:

Why Penrose is one of many crackpots when it comes to inflation

1 comment:

  1. Anonymous9:38 AM

    Scientific explanation as a compression of information

    Lubos Motl:Let me mention that Moshe Rozali's comments from a thread about naturalness of inflation were the driver that inspired me to write this text. At Cosmic Variance, he was explaining to other readers that cosmic inflation makes the evolution of the early Universe much more natural but strictly speaking, it is not necessary if you don't care about naturalness: