3D near-de Sitter gravity and the soft mode of DSSYK

TL;DR

This paper establishes a dual gravity description of the soft mode in double-scaled SYK with a time-dependent coupling, linking it to 3D Einstein-de Sitter gravity and reproducing DSSYK entropy.

Contribution

It introduces a novel dual gravity framework for DSSYK soft modes using 3D Einstein-de Sitter gravity with specific boundary conditions.

Findings

Dual gravity system is 2+1D Einstein-de Sitter gravity with localized energy on a dS2 slice.

Effective SYK equations match Israel junction conditions in the dual gravity.

Schwarzschild-de Sitter entropy calculation reproduces DSSYK entropy.

Abstract

We present a dual gravity interpretation of the complex reparametrization mode $\psi(u)$ that governs the soft dynamics of double-scaled SYK in the presence of a time-dependent Maldacena-Qi coupling. We find that the dual gravity system takes the form of 2+1-dimensional Einstein-de Sitter gravity with an energy distribution localized on a dS$_2$ slice within dS$_3$. The effective SYK equations of motion take the form of the Israel junction conditions across the dS$_2$ slice. We study the 1D effective action of the SYK soft mode and show that it coincides with the effective action derived from 3D Einstein-de Sitter gravity with conformal boundary conditions on $\mathscr{I}^\pm$. The boundary conditions split $\mathscr{I}^\pm$ into two hyperbolic $k=-1$ slices, and the holographic screen is placed at the intersection. We adapt the Gibbons-Hawking calculation of the Schwarzschild-de Sitter entropy to the case with $k=-1$ boundary conditions and find that it reproduces the semiclassical DSSYK entropy. The boundary-to-boundary Green functions in 3D de Sitter are equal to the square of DSSYK two-point functions. We give an alternative holographic interpretation of our results in terms of 3D AdS gravity with two time directions.