Equation-of-State Parameter for Reheating

Understand

Constraints to the parameters of inflation models are often derived assuming some plausible range for the number--e.g., $N_k=46$ to $N_k=60$--of $e$-folds of inflation that occurred between the time that our current observable Universe exited the horizon and the end of inflation.

• However, that number is, for any specific inflaton potential, related to an effective equation-of-state parameter $w_{\mathrm{re}}$ and temperature $T_{\mathrm{re}}$, for reheating.
• Although the physics of reheating is highly uncertain, there is a finite range of reasonable values for $w_{\mathrm{re}}$.
• Here we show that by restricting $w_{\mathrm{re}}$ to this range, more stringent constraints to inflation-model parameters can be derived than those obtained from the usual procedure.