Gravitational Condensate Stars: An Alternative to Black Holes

Round 1

Reviewer 1 Report

The manuscript is a refreshed version of the arXiv preprint gr-qc/0109035 in which it was presented the gravitational condensed star model, nowadays known as gravastar. Over the last two decades, this black-hole mimicker has gained popularity and has been widely investigated, collecting more than 400 citations according to the Inspire database. The manuscript also includes a nice appendix which summarises the most significant developments.

I am happy to say that this paper merits to be published and should be moved to production rapidly.

I just have some minor remarks.

Even when not referring to a cross-referenced equation, the authors use often (but not always) eq. and eqs.

In few recurrences they refer to the manuscript as 'Letter'.

In line 44, the authors refer to eq. (3) which is introduced later in Section 1. I would remove the cross-reference, but in the beginning of Section 1 I would write down the stress-energy tensor. It is a standard result and not absolutely necessary but it would ease the reading. (And the paragraph below Eq. (4) would be almost automatic.)

Units as cm are not followed by a full stop, see line 145.

In line 148, the authors write "we have introduced G for dimensional reasons" but I thought that they worked in units such that only c=1.

In Appendix A.6, the authors acknowledge the contribution to gravitational-wave science to the LIGO collaboration solely. I think it is unfair towards the Virgo collaboration and could produce a damaging narrative.

There is some confusion with abbreviations. I would personally remove the list of abbreviations and define them at the first occurrence. Some, e.g. BEC in the main matter and E/M in the appendix are used but not defined; others are listed at the end of the main matter but not used, e.g. GR; GBEC is defined twice; others, e.g. EOS for equation of state could be introduced. In line 297 it would be better to write explicitly ITP (UCSB).

I have also spotted some typos, mostly in the appendix, e.g. atmsophere, th, timecale, electromganetic.

Author Response

Please see the attached pdf file, ReplytoReviewer1.pdf

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors have proposed new final endpoint of complete gravitational collapse by extending the concept of Bose-Einstein condensation to gravitational systems, They have obtained the resulting collapsed cold, compact object has no singularities, event horizons, and a globally defined Killing time. The formulation and the analysis are correct and the presentation is good. I recommend the acceptance of the paper with some minor suggestions:

(1) Some recent references on the research problem should be added (e.g. Phys. Rev. D 102, 024037 (2020))

(2) There are some typos in the  manuscript which should be taken care.

(3) In Sec-3, the authors have shown the stability of the model. It will be interesting to the readers if the authors mention some other stability approaches (no need of detail working) can be feasible in the study.

Author Response

Please see attached file, ReplytoReview2.pdf

Author Response File: Author Response.pdf