Bulk interpretation of instanton contributions to JT length overlaps

Ascertain the bulk gravitational interpretation of the nonperturbative instanton corrections in the JT gravity matrix integral that govern the behavior of the length-basis overlap ⟨ℓ|V†V|ℓ′⟩ at lengths ℓ of order e^{S0}, including the origin of the exponential growth and oscillatory sign changes reported for large ℓ.

Background

The paper shows that beyond the universal Airy regime, negative-energy effects are captured by nonperturbative instanton contributions to the JT gravity matrix integral. These effects lead to a striking large-ℓ behavior of the length-basis overlap, including exponential growth and oscillations, as summarized in equation (instanton).

While the boundary (matrix integral) origin of these instanton corrections is understood, a clear bulk (geometric/path-integral) interpretation is not provided in the paper, and the authors explicitly defer a detailed bulk understanding.

References

We leave a detailed bulk understanding of these instanton contributions to future work.

— Negative energies and the breakdown of bulk geometry  (2603.25782 - Preskill et al., 26 Mar 2026) in Section 3.2, Non-perturbative instantons (ℓ ∼ e^{S0})

An open question is whether this combinatorial description extends beyond the perturbative genus expansion and admits a microscopic interpretation.

— Spacetime topology and geometry in JT Gravity from non-crossing permutations  (2609.28846 - Asplund et al., 23 Sep 2026) in Discussion section