Instantons near a tachyonic top in anti de Sitter and the no-boundary regulator

Understand

We investigate instantons near a tachyonic top in an anti de Sitter (AdS) background.

• If the mass scale around the hill-top is above the Breitenlohner-Freedman (BF) bound, then the top is classically stable.
• When the BF bound is satisfied, it is already known that there can exist instantons with a non-zero probability, though fine-tunings of the potential are required.
• On the other hand, we may consider a possibility to obtain instantons with a non-zero probability for more natural shape of potentials.