Description
The (H-H) no boundary proposal is a very natural and mathematically elegant proposal for computing the wavefunction of the universe. Although this proposal has existed since 1990, it is not clear how to get it as a saddle geometry of the quantum gravity path integral. In the first part of the talk, I will briefly describe how to get that following the recent work and our work as well. I will use the Picard-Lefschetz method and the Lorentzian contour prescription. I will also emphasise the importance of the initial boundary choices which leads to no boundary.
In the second part of my talk, I will focus on the small fluctuation around the no-boundary universe (going beyond minisuperspace). While it is well known that such fluctuations are Gaussian and hence akin to the BD-vacuum, the one-loop properties are not so well known. I will describe, following our work, the one-loop computation around such geometry. It turns out that one-loop effects (virtual graviton contribution) grow as the universe expands, overpowering the leading order. We see it as a signature of IR-divergence, characteristics in de-Sitter space.
Session Chair : Gaurav Narain
