May 6 – 10, 2024
US/Eastern timezone

The Bounce in the Bianchi models as a quantum scattering

May 7, 2024, 5:00 PM
15m
FAU FTL Room 312

FAU FTL Room 312

Cosmology, Black Holes, and other applications/phenomenology Cosmology

Speaker

Eleonora Giovannetti (CPT Marseille)

Description

We provide a new picture for the emergence of a bouncing cosmology at a pure quantum level, according to the idea that a semiclassical behavior of the Universe towards the singularity is not available in many relevant Minisuperspace models. In particular, we clarify how any Bianchi I localized wave packet unavoidably spreads when the singularity is approached, and therefore the semiclassical description of the model in the Planckian region loses its predictability, especially when the generic cosmological solution is taken into account. Then, we highlight the isomorphism between the Wheeler-DeWitt equation for the Bianchi models in the Misner variables and the Klein-Gordon equation for a relativistic scalar field. In particular, we identify the positive and negative frequency solutions with the collapsing and expanding Universe respectively. Then, we calculate the transition amplitude between a collapsing Universe and an expanding one for the Bianchi I model, according to the standard techniques of relativistic quantum mechanics, thanks to the introduction of an ekpyrotic-like matter component which mimics a time-dependent potential term and breaks the frequency separation. In particular, the transition probability of this "Quantum Big Bounce" shows the same symmetrical reconnection of the semiclassical bouncing cosmology. The same technique is improved by using the Dirac equation, in order to solve some issues related to the Klein-Gordon equation. This new approach is well adapted also to the study of the Kasner transition in the BKL map of the Bianchi IX model, in which the time-dependent potential is naturally present by construction and depends on the gravitational degrees of freedom.

Author

Eleonora Giovannetti (CPT Marseille)

Presentation materials