17 The Inflationary Universe
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Could one argue that the matter was put there by some unknown hand in
the beginning and we see it today? That idea would also be untenable if the
inflationary picture is correct. The point is that at the beginning of the Hubble
expansion after inflation ended, there was hardly any matter or anti-matter in
the universe (or at least whatever there was too highly diluted to be of any
consequence). Inflation essentially “vacuum cleans” the universe of all matter
due to its huge sudden expansion. So where did matter really come from,
and at what point in the evolution of the universe was this matter created?
Some believe that the neutrino story may also have something to do with that,
although it is far from clear that this is the real theory, since there are many
plausible ways to generate matter–anti-matter asymmetry. We discuss this in
Chap. 23.