- #1
Cerenkov
- 274
- 53
Hello.
I have some questions regarding Alan Guth's book on the Inflationary Universe.
The following, from pages 185 & 186, has piqued my interest. I have reproduced Figure 10.6, above. Please read on. My questions follow. Please also take note that I can only understand these matters at a basic level and would appreciate any answers at that level. Thank you.Implicit in Figure 10.6 is a remarkable prediction of the inflationary theory. Due to the enormous expansion during the inflationary period, the size of the observed universe before inflation was absurdly small. There is no reason, however, to suppose that the size of the entire universe was this small. While inflationary theory allows a wide variety of assumptions concerning the state of the universe before inflation, it seems very plausible that the size of the universe was about equal to the speed of light times its age, or perhaps even larger. If the universe were smaller than this, then it almost certainly would have already collapsed into a crunch.
Applying this reasoning to the sample numbers shown on Figure 10.6, we find that the entire universe is expected to be at least 1023 times larger than the observed universe!
These numbers are highly uncertain, since they depend sensitively on the duration of the period of inflation, which in turn depends on the decay rate of the false vacuum. Without knowing the correct grand unified theory and the values of all its parameters, the decay rate of the false vacuum cannot be even approximated. Nonetheless, the qualitative behavior shown in Figure 10.6 seems to be typical of all inflationary universe calculations. If the inflationary theory is correct, then the observed universe is only a minute speck in a universe that is many orders of magnitude larger.In a footnote Guth writes that the ratio between the size of the observed universe and the size of the entire universe would persist after the inflationary phase. So today the entire universe would still be at least 1023 times larger than the observed universe.
Now to my questions.
1.
Given that all of the above dates from 1998, has any subsequent data called it into question? I ask because I’ve read that the WMAP and Planck CMB data did indeed rule out some early inflationary models.2.
Given the vintage of Guth’s statements, is his claim about the qualitative behavior of Figure 10.6 seeming to be typical for all inflationary universe calculations, still valid?3.
Is the ratio cited above still an accepted part of current inflationary theory or has it been superseded or ruled out in some way?4.
Is the persistence of this ratio after the inflationary period still part of current inflationary theory?5.
Guth posits that the early universe would have collapsed into a crunch if it were any smaller than the value he uses in his calculation. Is this line of reasoning still part of current inflationary theory?6.
Given the highly uncertain nature of the values used in Guth’s calculations, in your opinion, is his claim that the entire universe would still be at least 1023 times larger than the observed universe?
A. Wishful thinking.
B. Informed speculation.
C. Something else (please specify).
Thanks in advance,
Cerenkov.