Power-law inflation
= Power-law inflation
{title2=$a(t)\propto t^p,\quad p>1$}
<Power-law inflation> is <cosmic inflation> with a <scale factor> proportional to $t^p$ for constant $p>1$. Its <Hubble parameter> is $H=p/t$ and its <first Hubble slow-roll parameter> is $\epsilon_H=1/p$. The <comoving Hubble radius> decreases as $t^{1-p}$. A canonical <inflaton> with an exponential <inflaton potential> admits an exact example. Because $\epsilon_H$ is constant, an indefinitely maintained power law has no <graceful exit from inflation>.