Conformal bootstrap for surfaces with boundary in Liouville CFT. Part 1: Segal axioms

This paper is the first part of the proof of the conformal bootstrap for Liouville conformal field theory on surfaces with a boundary, devoted to Segal’s axioms in this context. We introduce the notion of Segal’s amplitudes on surfaces with corners and prove the gluing property for such amplitudes. The semigroup of half-annuli and its generator are studied and we develop the necessary material for proving its spectral decomposition using scattering theory in a companion paper. The Segal gluing properties and the spectral decomposition allow us to prove the conformal bootstrap formula for correlation functions of Liouville conformal field theory with a boundary. This has several important applications to the study of conformal blocks (analyticity and convergence) in Ghosal, Rémy, Sun, and Sun [ Analyticity and symmetry of Virasoro conformal blocks via Liouville CFT , 2023], in the construction of a unitary representation of mapping class group in the space of conformal blocks, and the study of random moduli in Ang, Remy, and Sun [Ann. Sci. Éc. Norm. Supér. (4) 58 (2025), pp. 1037–1087] in Liouville quantum gravity.