Infrared signatures of quantum bounce in a minisuperspace analysis of Lema\^{\i}tre-Tolman-Bondi dust collapse

TL;DR

This paper investigates the infrared signatures of quantum bounce phenomena in a spherically symmetric dust collapse model, revealing how bounce information is encoded in long-wavelength modes before classical singularity resolution.

Contribution

It introduces a mode decomposition method in a quantum Lemaître-Tolman-Bondi model, linking infrared radiation features to the bounce dynamics and operator ordering ambiguities.

Findings

Infrared modes are highly sensitive to near-bounce dynamics.

A flip from incoming to outgoing radiation encodes bounce information.

Long-wavelength modes carry signatures of short-scale physics.

Abstract

In the quantum treatment of collapsing matter, a viable mode analysis is supposed to give information regarding emission during the collapse. Nevertheless, partly owing to operator ordering ambiguities involved in a typical quantum gravity analysis, the availability of such well-defined modes is not guaranteed. We study the mode decomposition of the unitarily evolving wave packet constructed for the quantum model of spherically symmetric dust collapsing in a marginally bound Lema\^{\i}tre-Tolman-Bondi (LTB) model. We identify the observable depicting mode decomposition, and using the freedom of operator ordering ambiguity, we obtain the Hermitian extension of this operator alongside the Hermitian Hamiltonian. After identifying incoming and outgoing modes with this operator's eigenstates, we estimate their contributions to the radiation profile. The infrared sector of this process demonstrates some characteristic features which turn out to be highly sensitive to the near-bounce dynamics of the dust cloud. Near the epoch of classical singularity, there is a significant contribution from incoming/outgoing modes of small wavenumber in the expanding/collapsing phase of the dust cloud, which keeps on decreasing as one moves away from the singularity. The information of the bounce is carried over to the infrared modes through a flip from largely incoming to largely outgoing radiation as the evolution progresses from collapsing to expanding phase, much before the information of bounce comes about to any observer. In the infrared sector, the saturation value of the amplitude marks the bounce radius. Thus, we argue that the information of the short scale physics is essentially carried over to the longest wavelength in this quantum gravity model, which we argue is rather more prominent for low energy processes.