Consequences of the Improved Limits on the Tensor-to-Scalar Ratio from BICEP/Planck, and of Future CMB-S4 Measurements, for Inflationary Models
Round 1
Reviewer 1 Report
This work is an actualization of the previous work of the authors [1], on the predictions of a series of inflationary models, and their consistency with recent observational constraints, and in certain cases, with constraints expected to come. The analysis is extensive and detailed and considers mainly the tensor-scalar ratio, as well as the scalar spectral index and its running.
My comment is that it would be helpful a discussion on the selection criteria for the models, and regarding omitted relevant models, like modified gravity.
Otherwise I recommend the publication of the article.
Author Response
Citation: “This work is an actualization of the previous work of the authors [1], on the predictions of a series of inflationary models, and their consistency with recent observational constraints, and in certain cases, with constraints expected to come. The analysis is extensive and detailed and considers mainly the tensor-scalar ratio, as well as the scalar spectral index and its running.
My comment is that it would be helpful a discussion on the selection criteria for the models, and regarding omitted relevant models, like modified gravity.
Otherwise I recommend the publication of the article.”
Answer: In the summary I have now included the following text: The present work has been concerned with observational constraints on inflationary models coming from measurements of the spectral index of the cosmic microwave radiation and the tensor to scalar ratio. The dominating selection criterion in this connection is that in order to be an acceptable inflationary model, the predictions of the model must not be in conflict with the observational data. But there exist several inflationary models that are acceptable according to both the most recent observational data and future expected data from CMB-S4. Then we need additional criteria for selecting between these models. I have chosen a very conservative point of view, namely that inflationary models based upon the general theory of relativity are more acceptable that those based upon modified gravity, since all observational tests have favoured general relativity against modified gravitational theories. Hence I have mainly given focus to general relativistic inflationary models in this paper. There are many inflationary models based upon modified gravity [79, 80], and even the Starobinsky model can be interpreted in this way. I have included two more references in the revised version of the paper on inflationary models based on modified gravity theories.
- K. Bamba and S. D. Odintsov. “Inflationary Cosmology in Modified Gravity Theories.” Symmetry 2015, 7, 220-240; doi:10.3390/sym7010220.
- X. Zhang, Che-Yu Chen, and Y. Reyimuaji. “Modified gravity models for inflation: In conformity with observations.” Phys. Rev. 2022, D 105, 043514.
Reviewer 2 Report
The author solves for different models of Inflation the observables. The paper is interesting and involves many models inside. My main concern is about the novelty of the models/the results.
Author Response
Citation: “The author solves for different models of Inflation the observables. The paper is interesting and involves many models inside. My main concern is about the novelty of the models/the results.”
Anwer: This is a review paper with some new results. It reviews the results of my more than 150 sides long paper (ref. [1]) and makes the main results of that paper more readable by presenting them in a paper with the fifth of the length of the previous paper. The new results here are 1. The inflationary models are confronted with the new restrictions from the Planck collaboration (ref. 4). 2. I discuss what we can expect from the large future project CMB-S4 (Cosmic Microwave Background Stage 4) on the work of eliminating inflationary models that do not correspond with what actually happened in the first moments of the evolution of our universe.
Reviewer 3 Report
I read the entire manuscript for 5 days and actually went through the review of the different cosmological models
One criticism, but it is not a reason to reject the manuscript: On lines 522 to 530 the author introduces what is called "warm inflation". I frankly had never heard of this one before and spent hours over this section of the manuscript. On lines 536 to 549 there is a development mentioned as to how Warm inflation compares with "cold inflation" . I found the citing of equation in line 566 important , but then the line 567 to 569 to be a bit terse. and under developed. As I am certain that most cosmologists have never heard of this version of inflation, I would appreciate more explanation and development. These lines, 567 to 569 are hugely important. In addition on lines 571 to 572 there is a comment that if N = 50 , etc this is a "promising model" (this on line 572) . Frankly Why is this the case ?
In lines 596 - 602 , there is no explanation given as to why the caveats given in lines 600 to 602 are true. I tried to derive this one for 4 hours , then gave up and left it as a forward to the author to consider.
On line 637 the author states that "tachyon warm intemediate brane inflation " is in line with the BICEP 2 data
Dumb question. Does this mean that "Tachyon warm intermediate brane inflation" is a favored model , over say Starobinskiy style classical inflation ? Just how significant is "tachyon warm intermediate brane inflation " and is this a model which deserves particular emphasis and future development in the view of the author ?
Author Response
Se attached pdf-file
Author Response File: 
Author Response.pdf
