# Cosmic Censorship of Trans-Planckian Field Ranges in Gravitational Collapse

### Submission summary

 As Contributors: Chethan Krishnan Arxiv Link: https://arxiv.org/abs/2003.05488v3 (pdf) Date accepted: 2020-08-25 Date submitted: 2020-08-11 11:39 Submitted by: Krishnan, Chethan Submitted to: SciPost Physics Discipline: Physics Subject area: High-Energy Physics - Theory Approach: Theoretical

### Abstract

A classical solution where the (scalar) field value moves by an ${\cal O}(1)$ range in Planck units is believed to signal the breakdown of Effective Field Theory (EFT). One heuristic argument for this is that such a field will have enough energy to be inside its own Schwarzschild radius, and will result in collapse. In this paper, we consider an inverse problem: what kind of field ranges arise during the gravitational collapse of a classical field? Despite the fact that collapse has been studied for almost a hundred years, most of the discussion is phrased in terms of fluid stress tensors, and not fields. An exception is the scalar collapse made famous by Choptuik. We re-consider Choptuik-like systems, but with the emphasis now on the evolution of the scalar. We give strong evidence that generic spherically symmetric collapse of a massless scalar field leads to super-Planckian field movement. But we also note that in every such supercritical collapse scenario, the large field range is hidden behind an apparent horizon. We also discuss how the familiar perfect fluid models for collapse like Oppenheimer-Snyder and Vaidya should be viewed in light of our results.

Published as SciPost Phys. 9, 036 (2020)

We thank the referee for the report and the comments. We have made the following minor changes as suggested by the referee --

### List of changes

1. In the earlier version, we had alluded to the case of multiple fields and non-canonical kinetic terms as a part of one of the final paragraphs of the paper. Now we have added a couple of more sentences, to emphasize the point referee makes. See the third last paragraph on p.14.

2. (a) We have added the references that the referee pointed out regarding the "heuristic black hole argument" (HBHA), and edited footnote 3.

(b) We have mentioned [8] and the other three references pointed out by the referee, separately at the end of the paragraph that discussed the HBHA. The three references are now also mentioned as part of the conclusion, in the relevant paragraph.

3. We have added the name of author and title to reference [27] (previously ref [21]).