A tale of two saddles

  title={A tale of two saddles},
  author={Venkat Chandrasekaran and Netta Engelhardt and Sebastian Fischetti and Sergio Hernandez-Cuenca},
  journal={Journal of High Energy Physics},
We find a new on-shell replica wormhole in a computation of the generating functional of JT gravity coupled to matter. We show that this saddle has lower action than the disconnected one, and that it is stable under restriction to real Lorentzian sections, but can be unstable otherwise. The behavior of the classical generating functional thus may be strongly dependent on the signature of allowed perturbations. As part of our analysis, we give an LM-style construction for computing the on-shell… 



Free energy from replica wormholes

Euclidean wormholes---geometries which connect disconnected boundaries---present a challenge to a standard quantum mechanical interpretation of the theory. One potential resolution is that the

Replica wormholes and the entropy of Hawking radiation

The information paradox can be realized in anti-de Sitter spacetime joined to a Minkowski region. In this setting, we show that the large discrepancy between the von Neumann entropy as calculated by

The path integral of 3D gravity near extremality; or, JT gravity with defects as a matrix integral

We propose that a class of new topologies, for which there is no classical solution, should be included in the path integral of three-dimensional pure gravity, and that their inclusion solves

Replica wormholes and the black hole interior

Recent work has shown how to obtain the Page curve of an evaporating black hole from holographic computations of entanglement entropy. We show how these computations can be justified using the

Free partition functions and an averaged holographic duality

We study the torus partition functions of free bosonic CFTs in two dimensions. Integrating over Narain moduli defines an ensemble-averaged free CFT. We calculate the averaged partition function and

Gravity factorized

We find models of two dimensional gravity that resolve the factorization puzzle and have a discrete spectrum, whilst retaining a semiclassical description. A novelty of these models is that they

Matrix models and deformations of JT gravity

  • E. Witten
  • Physics
    Proceedings of the Royal Society A
  • 2020
It is argued that a deformation of JT gravity with bulk action −1/2∫d2xg( ϕR+W(ϕ)) is likewise dual to a matrix model, and the density of eigenvalues of the dual matrix model is determined.

Transcending the ensemble: baby universes, spacetime wormholes, and the order and disorder of black hole information

In the 1980’s, work by Coleman and by Giddings and Strominger linked the physics of spacetime wormholes to ‘baby universes’ and an ensemble of theories. We revisit such ideas, using features

Gravity/ensemble duality

For the first time, a gravitational calculation was recently shown to yield the Page curve for the entropy of Hawking radiation, consistent with unitary evolution. However, the calculation takes as

Narain to Narnia

We generalize the holographic correspondence between topological gravity coupled to an abelian Chern–Simons theory in three dimensions and an ensemble average of Narain’s family of massless free