Résumé / Abstract Journal-club_GReCO

Séminaire / Seminar GReCO

« Using a Born-Oppenheimer approach for canonical quantum gravity and the emerging dynamics »

Giulia Maniccia
Univ. Rome La Sapienza (Rome, Italie)

The quantization of the gravitational field is a rather complex issue, starting from the first attempt of the Wheeler-DeWitt theory. Indeed, the Hamiltonian formalism of gravity leads to constraints, deriving from general covariance, and its canonical quantization causes the so-called problem of time. A procedure to overcome such issue, while also providing a mean of investigation for quantum-gravity-induced effects on quantum field theory on curved spacetime, is based on a Born-Oppenheimer separation of the system. Indeed, the "slow" gravitational sector is described differently from the "fast" matter one, being both of them quantum. Then, through a Wentzel-Kramer-Brillouin expansion of the system wave function, it is possible to investigate corrections to the standard QFT dynamics in a functional approach. On the cosmological level, such corrections could bring new effects at the early stage of our Universe.
In this seminar I will show two clock constructions, linked to a "materialization" of the reference frame, and discuss how they imply unitarity at the next order. I will provide a cosmological example where the two formulations turn out to be equivalent. I will also discuss the importance of the gauge invariance related to the Born-Oppenheimer factorization, when requiring initial constraints for the gravitational
jeudi 5 octobre 2023 - 11:00
Salle 281
Institut d'Astrophysique de Paris
Pages web du séminaire / Seminar's webpage