Thermalization in Quenched De Sitter Space

Submission summary

 As Contributors: Sayantan Choudhury Arxiv Link: https://arxiv.org/abs/2104.10692v4 (pdf) Date submitted: 2021-12-12 14:39 Submitted by: Choudhury, Sayantan Submitted to: SciPost Physics Academic field: Physics Specialties: Gravitation, Cosmology and Astroparticle Physics High-Energy Physics - Theory Approach: Theoretical

Abstract

In this article, we study the quantum field theoretic generalization of the Caldeira-Leggett model in general curved space-time considering interactions between two scalar fields in a classical gravitational background. The thermalization phenomena is then studied from the obtained de Sitter solution using quantum quench from one scalar field model obtained from path integrated effective action in Euclidean signature. We consider an instantaneous quench in the time-dependent mass protocol of the field of our interest. We find that the dynamics of the field post-quench can be described in terms of the state of the generalized Calabrese-Cardy (gCC) form and computed the different types of two-point correlation functions in this context. We explicitly found the conserved charges of $W_{\infty}$ algebra that represents the gCC state after a quench in de Sitter space and found it to be significantly different from the flat space-time results. We extend our study for the different two-point correlation functions not only considering the pre-quench state as the ground state, but also a squeezed state. We found that irrespective of the pre-quench state, the post quench state can be written in terms of the gCC state showing that the subsystem of our interest thermalizes in de Sitter space. Furthermore, we provide a general expression for the two-point correlators and explicitly show the thermalization process by considering a thermal Generalized Gibbs ensemble (GGE). Finally, from the equal time momentum dependent counterpart of the obtained results for the two-point correlators, we have studied the hidden features of the power spectra and studied its consequences for different choices of the quantum initial conditions.

Current status:
Editor-in-charge assigned

Submission & Refereeing History

Submission 2104.10692v4 on 12 December 2021

Reports on this Submission

Strengths

Writing is clear at a technical level

Weaknesses

The motivation is poor

Report

This paper studies quantum quenches for fields in de Sitter spacetime. While the calculations appear correct, the big problem with the paper is that there is little explanation for why one should study quantum quenches in de Sitter spacetime. There is some mention at the beginning about this relating to fast phase transitions in the early universe, but that's all. It's very slim motivation given that there is then well over 100 pages devoted to the subject.

Moreover, it's quite difficult to think of a genuine motivation for these calculations. The usual phase transitions that take place in the early universe arise because of the expansion of the universe and the related cooling. There is nothing fast about this. The time scale of the phase transition is set by the inverse Hubble scale. Here, the idea is that there is out-of-equilibrium dynamics taking place in the early universe in a smooth de Sitter background and there seems little reason to think that this is an interesting thing to study.

My impression is that the real reason the author's explored this is because there were calculations that they could do. But this is not enough to warrant publication in a top journal like SciPost. For that reason, I recommend that this paper is rejected.

• validity: good
• significance: poor
• originality: low
• clarity: ok
• formatting: -
• grammar: -

Report

See the attached file.

Attachment

• validity: -
• significance: -
• originality: -
• clarity: -
• formatting: -
• grammar: -