Eternal Inflation is "Expensive"

Understand

The discovery of the string theory landscape has recently brought attention to the eternal nature of inflation.

• In contrast to the common belief that eternal inflation may be a generic feature of most inflationary models, in this note we argue that the suppressed amplitude of perturbations due to adiabatic regularization, together with a fine-tuning constraint on the equation of state of the rare inflating pockets with large fluctuations, render eternal inflation expensive in energy and may make it unlikely to occur.
• The energy scales of the eternally inflating pockets have to be very close to the transplanckian regime in order to compensate for the suppression of regularized perturbations.