2025年
10/21
開催
開催日時
2025/10/21（火）11:00〜12:00
開催場所
研究本館セミナールームとzoom
講演者
Wolfgang Wieland (Erlangen-Nuremberg U., IQG)
言語
英語
概要
This presentation gives an outline of a research programme in quantum gravity to investigate how a discrete area spectrum can affect the quantization of gravitational null (light-like) initial data. The starting point is a non-perturbative characterization of the gravitational phase space on a null boundary for tetradic gravity with the parity violating γ-term (Holst term) in the action. Then, the description is taken to the quantum level. Starting from the standard canonical quantisation of the classical phase space, a model of a quantum null geometry is found. The spatial sections of the three-dimensional null initial surface are thereby tessellated into a fixed number of plaquettes. Each of these plaquettes carries a CFT.
Operators in this CFT characterize the quantum geometry of the null surface; including its shear and expansion. Depending on the value of the central charge of the CFT, two regimes can be distinguished. There is an infra-Planckian regime in which the central charge is positive and an ultra-Planckian regime in which it is negative. A negative central charge is problematic because it is a strong indication for a non-unitary CFT, which has no positive-definite inner product on its physical state space. For an asymptotic boundary, the two regimes are separated by the Planck power. Below the Planck power, the spectrum of the radiated power is discrete and the central charge is positive.
Above the Planck power, the central charge is negative. The results of this research suggest a potential quantum gravity effect that creates an upper bound for the radiated power. The talk is based on arXiv:2402.12578, arXiv:2401.17491, arXiv:2104.05803.