
TL;DR
This paper demonstrates that fast-roll inflation, a non-slow-roll regime where |m^2| is not much less than H^2, can be long-lasting and may set initial conditions for slow-roll inflation or explain current cosmic acceleration.
Contribution
It introduces the concept of fast-roll inflation in simple symmetry-breaking theories and explores its implications for early universe conditions and late-time acceleration.
Findings
Fast-roll inflation can last long if |m| is small.
It can serve as initial conditions for slow-roll inflation.
The universe cannot reach anti-de Sitter regime after inflation.
Abstract
We show that in the simplest theories of spontaneous symmetry breaking one can have a stage of a fast-roll inflation. In this regime the standard slow-roll condition |m^2| << H^2 is violated. Nevertheless, this stage can be rather long if |m| is sufficiently small. Fast-roll inflation can be useful for generating proper initial conditions for the subsequent stage of slow-roll inflation in the very early universe. It may also be responsible for the present stage of accelerated expansion of the universe. We also make two observations of a more general nature. First of all, the universe after a long stage of inflation (either slow-roll or fast-roll) cannot reach anti-de Sitter regime even if the cosmological constant is negative. Secondly, the theories with the potentials with a "stable" minimum at V(\phi)<0 in the cosmological background exhibit the same instability as the theories with…
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