Pacman geometries and the Hayward term in JT gravity

TL;DR

This paper explores the role of the Hayward term in JT gravity, analyzing its effects on boundary corners, conical defects, and entropy calculations, revealing new insights into gravitational edge modes and defect operators.

Contribution

It demonstrates the necessity of the Hayward term for correct entropy spectra, connects it with cosmic branes, and clarifies the nature of conical defects in JT gravity.

Findings

Hayward term is essential for flat Rb9nyi entropy spectrum

Conical defects differ from pointlike sources studied previously

Derived the area operator within the gravitational modular Hamiltonian

Abstract

We study the Hayward term describing corners in the boundary of the geometry in the context of the Jackiw-Teitelboim gravity. These corners naturally arise in the computation of Hartle-Hawking wave functionals and reduced density matrices, and give origin to AdS spacetimes with conical defects. This set up constitutes a lab to manifestly realize many aspects of the construction recently proposed in \cite{Botta2020}. In particular, it can be shown that the Hayward term is required to reproduce the flat spectrum of R\'enyi entropies in the Fursaev's derivation, and furthermore, the action with an extra Nambu-Goto term associated to the Dong's cosmic brane prescription appears naturally. On the other hand, the conical defect coming from Hayward term contribution are subtly different from the defects set as pointlike \emph{sources} studied previously in the literature. We study and analyze these quantitative differences in the path integral and compare the results. Also study previous proposals on the superselection sectors, and by computing the density operator we obtain the Shannon entropy and some novel results on the symmetry group representations and edge modes. It also makes contact with the so-called \emph{defect operator} found in \cite{Jafferis2019}. Lastly, we obtain the area operator as part of the gravitational modular Hamiltonian, in agreement with the Jafferis-Lewkowycz-Maldacena-Suh proposal.