  Thermalons can mediate phase transitions between different vacua in higher
curvature gravity, potentially changing the asymptotic structure of the
spacetime. Treating the cosmological constant as a dynamical parameter, we
study these phase transitions in the context of extended thermodynamic phase
space. We find that in addition to the AdS to dS phase transitions previously
studied, thermal AdS space can undergo a phase transition to an asymptotically
flat black hole geometry. In the context of AdS to AdS transitions, we comment
on the similarities and differences between thermalon transitions and the
Hawking-Page transition.
