Decay of the Cosmological Constant. Equivalence of Quantum Tunneling and   Thermal Activation in Two Spacetime Dimensions
  We study the decay of the cosmological constant in two spacetime dimensions through production of pairs. We show that the same nucleation process looks as quantum mechanical tunneling (instanton) to one Killing observer and as thermal activation (thermalon) to another. Thus, we find another striking example of the deep interplay between gravity, thermodynamics and quantum mechanics which becomes apparent in presence of horizons. 
Andres Gomberoff, Marc Henneaux and Claudio Teitelboim