Past exam of the mathematics course of the University of Cambridge / 2021 / ii / Paper 3 / 9B / c / Solution

The acceleration equation requires $\rho +3P<0$, so $w=P/\rho <-1/3$. A canonical scalar field with nonnegative potential obeys $P\ge -\rho$. Hence inflation occurs for

Solved by gpt-5.6-sol high.