JT de Sitter Gravity as a Model of Coleman-de Luccia Tunneling
Sidan A, Tom Banks
TL;DR
We propose that the Euclidean JT de Sitter solution acts as a Coleman-de Luccia instanton for decays of a low-entropy static patch into either a Big Crunch or an expanding de Sitter cosmology, with entropy governed by the Covariant Entropy Principle $S = \frac{A_{\diamond}}{4 G_N}$. The two Lorentzian continuations correspond to a high-entropy expanding phase and a finite-entropy Crunch, with detailed balance constraining transition probabilities. A broad class of large-N fermionic oscillator models is constructed to reproduce the JT dS dynamics, using unitary embeddings of nested causal diamonds in a holographic space-time framework. The work links 1+1D JT gravity to causal-diamond hydrodynamics, modular theory, and entropy-driven cosmological transitions, and outlines future directions for coupling to matter and exploring infinite-entropy de Sitter limits.
Abstract
We interpret the Euclidean solution of JT de Sitter gravity as the Coleman-de Luccia instanton for the decay of the low-entropy horizon of its static patch solution into either a Big Crunch or an infinite-entropy Lorentzian de Sitter cosmology. As in previous work by one of the authors, the Big Crunch is interpreted as bounding the entropy of the static state. The principle of detailed balance then guarantees it will transition back to a higher entropy causal diamond in the expanding cosmology. We then construct a family of explicit quantum mechanical models and appropriate metastable states, with transition probabilities well approximated by the semi-classical calculations in JT de Sitter gravity.