Cosmological Fluctuations in Delta Gravity
Round 1
Reviewer 1 Report
Manuscript ID: universe-2360535
In this work the authors compute the cosmological fluctuations in Delta Gravity that give
rise to the CMB. To achieve this goal they used a hydrodynamic approach,
The authors also present the equations of the evolution of cosmological fluctuations.
and present some properties of the solutions to obtain the scalar TT Power Spectrum. The authors provide useful expressions for temperature fluctuations, studying the propagation of photons in the resulting effective metric.
Furthermore, the results presented in this work may be used to compare the Delta Gravity theory with astronomical data.
The work is well written and self contained, the authors manage to present all the derivations in a straightforward way. The work may feel dense in some parts but the detailed explanations are in the end useful to understand the new mechanisms allowed by the approach. I would like the authors take the following minor points into consideration
* The definition of the effective metric, above Eq. 12 should be improved.
* The definition of the spatial metric, Eq. 14, is unclear.
* Could the authors rephrase the paragraph just above Eq. 20. Do the authors mean “The field equations” instead of GR equations?
* The definition of the functions in ·q. 33 and 34 are not provided.
* The authors mention they developed a more accurate numerical framework, however they do not mention what are the improvements, if any on the results.
If the authors may provide some insights on these points I would recommend the work for publication in Universe.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
In the present manuscript the implications of the first law of thermodynamics in a modified geometry is studied. Distinguishes between the physical densities and GR densities are shown. The theory of perturbations for Delta Gravity and its gauge transformations is developed. Equations for cosmological perturbations using the hydrodynamic approximation are calculated. It is found that an expression for temperature fluctuations in Delta Gravity and those temperature fluctuations split into three independent terms.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
see universe-2360535-rev.pdf in attachment
Comments for author File: Comments.pdf
see attached review where this issue is addressed
Author Response
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Round 2
Reviewer 3 Report
see universe-2360535-rev2.pdf
Comments for author File: Comments.pdf
Author Response
Please see the attachment
Author Response File: Author Response.pdf
