A non-rational Verlinde formula from Virasoro TQFT

Journal article

Abstract We use the Virasoro TQFT to derive an integral identity that we view as a non-rational generalization of the Verlinde formula for the Virasoro algebra with central charge c ≥ 25. The identity expresses the Virasoro fusion kernel as an integral over a ratio of modular S-kernels on the (punctured) torus. In particular, it shows that the one-point S-kernel diagonalizes the Virasoro 6j symbol. After carefully studying the analytic properties of this ‘Virasoro-Verlinde formula’, we present three applications. In boundary Liouville CFT, the formula ensures the open-closed duality of the boundary one-point function on the annulus. In pure 3d gravity, it provides an essential step in computing the partition function on hyperbolic 3-manifolds that fiber over the circle. Lastly, in AdS3/CFT2, the formula computes a three-boundary torus wormhole, which leads to a prediction for the statistical correlation between the density of states and two OPE coefficients in the dual large-c CFT ensemble. We conclude by discussing the implications of our result for the fusion rules in generic non-rational 2d CFTs.

Authors: Post, B; Tsiares, I

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Springer
• Journal: Journal of High Energy Physics
• Volume: 2025
• Issue: 4
• Article number: 15
• Publication date: 2025-04-01
• DOI: 10.1007/jhep04(2025)015
• EISSN: 1029-8479
• ISSN: 1126-6708
• Language: English
• Keywords: Mathematics; Pure mathematics; Topological quantum field theory