Comment on "Apparent horizons of the Thakurta spacetime and the description of cosmological black holes"

TL;DR

This paper clarifies discrepancies in the understanding of apparent horizons in Thakurta spacetime by analyzing coordinate transformations and providing explicit examples, thereby refining the description of cosmological black holes.

Contribution

It identifies the source of previous inconsistencies and offers a concrete example to distinguish horizons and spacetime regions in Thakurta spacetime.

Findings

Coordinate transformations can cover inaccessible spacetime regions.

Explicit example clarifies horizon and spacetime region distinctions.

Resolves previous inconsistencies in horizon analysis.

Abstract

The findings discussed in "Apparent Horizons of the Thakurta Spacetime and the Description of Cosmological Black Holes" deviate from prior research, particularly our study in Phys. Rev. D 95, 084031 (2017). We clarify this inconsistency, which arises from employing a coordinate transformation covering a distinct region of spacetime -- specifically one considered inaccessible due to its location beyond a singularity, making it unreachable from infinity. Additionally, we provide a concrete example where the distinct horizons and spacetime regions are readily discernible.