PIRSA:25100044

Video URL

https://pirsa.org/25100044

Unimodular Henneaux-Teitelboim (HT) Gravity: 4D and 2D applications

Alexandre, B.S.C. (2025). Unimodular Henneaux-Teitelboim (HT) Gravity: 4D and 2D applications. Perimeter Institute for Theoretical Physics. https://pirsa.org/25100044

Alexandre, Bruno S C. Unimodular Henneaux-Teitelboim (HT) Gravity: 4D and 2D applications. Perimeter Institute for Theoretical Physics, Oct. 14, 2025, https://pirsa.org/25100044 

          @misc{ scivideos_PIRSA:25100044,
            doi = {10.48660/25100044},
            url = {https://pirsa.org/25100044},
            author = {Alexandre, Bruno S C},
            keywords = {Cosmology},
            language = {en},
            title = {Unimodular Henneaux-Teitelboim (HT) Gravity: 4D and 2D applications},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2025},
            month = {oct},
            note = {PIRSA:25100044 see, \url{https://scivideos.org/index.php/pirsa/25100044}}
          }

Bruno S C Alexandre

Talk numberPIRSA:25100044
DOI10.48660/25100044
Source RepositoryPIRSA
Collection
Talk Type Scientific Series
Subject

Abstract

Unimodular Henneaux-Teitelboim (HT) Gravity provides a fully diffeomorphism-invariant route to unimodular gravity by promoting the cosmological constant to a conjugate variable with an associated “unimodular time”. I will present two complementary applications. In 4D minisuperspace, starting from the connection representation, unimodular Hartle–Hawking wave packets yield a unitary inner product and normalizable states whose peaks track classical FRW dynamics. This work reframes “creation from nothing” as the emergence of a semiclassical Universe from interference of incident/reflected packets near the bounce, without invoking Vilenkin’s contour. In parallel, I will introduce a 2D cousin obtained via a centrally extended JT/KSY construction. In de Sitter quantum cosmology, superposing Lambda-eigenstates produces unitary evolution in unimodular time, controlled interference near T=0, and sharply separated WKB branches at late times. The same mechanism naturally accommodates transient quantum deformations of global dS and suggests a topology change interpretation in which contracting/expanding branches play the role of Universe/anti-Universe pairs.