Talk:Infinite derivative gravity

The reference list to this class of theories is biased and incomplete. There are several papers where the same or a very similar action was proposed and that predate, depending on the case, all, most, or some of the cited references. Among many others:

Krasnikov, N.V. (1987). Nonlocal gauge theories, Theor. Math. Phys. 73, 1184. DOI:10.1007/BF01017588

Kuz'min, Y.V. (1989). The convergent nonlocal gravitation, Sov. J. Nucl. Phys. 50, 1011.

Tomboulis, E.T. (1997). Super-renormalizable gauge and gravitational theories, arXiv:hep-th/9702146.

Modesto, L. (2012). Super-renormalizable quantum gravity, Phys. Rev. D 86, 044005, arXiv:1107.2403. DOI:10.1103/PhysRevD.86.044005

Calcagni, G.; Modesto, L. (2015). Nonlocal quantum gravity and M-theory, Phys. Rev. D 91, 124059, arXiv:1404.2137. DOI:10.1103/PhysRevD.91.124059

Modesto, L.; Rachwal, L. (2014). Super-renormalizable and finite gravitational theories, Nucl. Phys. B 889, 228, arXiv:1407.8036. DOI:10.1016/j.nuclphysb.2014.10.015

Modesto, L.; Rachwal, L. (2015). Universally finite gravitational and gauge theories, Nucl. Phys. B 900, 147, arXiv:1503.00261. DOI:10.1016/j.nuclphysb.2015.09.006

not to mention several papers by Moffat and Cornish from the early 1990s. Plus Modesto's papers make a claim based on power counting renormalizability, this requires further checks. The authors assume the properties of local gauge theory in these papers which are not accepted by and large the community.

Furthermore, the issue of singularity removal is still under dispute in the community and the conclusions drawn by the author of this Wikipedia article do not reflect a universal consensus. Could you tell us who/which papers dispute these claims?

GotAlight (talk) 07:31, 25 April 2018 (UTC)
 * Thanks for this list, I will try and these papers to the article. Do you have access to translations of the first two papers? Absolutelypuremilk (talk) 08:47, 25 April 2018 (UTC)
 * The first one, by Krasnikov, has a DOI number with the paper in English. The second one, by Kuz'min, does not exist in digital form, as far as I know. Typically institutional libraries can get a scanned copy. Note that the first is mainly (but not exclusively) devoted to gauge theories, while the second is about gravity alone. GotAlight (talk) 09:14, 25 April 2018 (UTC)
 * GotAlight, do you have any more concerns about the article or can I remove the tag? Absolutelypuremilk (talk) 16:54, 27 May 2018 (UTC)

Thank you for implementing part of the suggested changes. I have the following remarks answering also your question:

- It is not correct that Modesto "studies only the power counting renormalizability" of the theory. There are several papers that perform a renormalizability analysis that goes far beyond power counting. The two papers by Modesto and Rachwal I mentioned in my first post are examples.

- If you compare the dates of your ref. 4 with 12, maybe one could say that the historical perspective given in this article is, to put it in a friendly way, "incomplete". This is not just a matter of refs. 4 and 12, as you probably already know.

- Concerning the debate about singularity resolution, there are a bunch of publications of authors not mentioned in the article. Among others:

Calcagni, G., Nardelli, G. (2010). Nonlocal gravity and the diffusion equation. Phys. Rev. D 82, 123518. DOI:10.1103/PhysRevD.82.123518. arXiv:1004.5144.

Calcagni, G., Modesto, L., Nicolini, P. (2014). Super-accelerating bouncing cosmology in asymptotically-free non-local gravity. Eur. Phys. J. C 74, 2999. DOI:10.1140/epjc/s10052-014-2999-8. arXiv:1306.5332.

Li, Y.D., Modesto, L., Rachwal, L. (2015). Exact solutions and spacetime singularities in nonlocal gravity. JHEP 1512, 173. DOI:10.1007/JHEP12(2015)173. arXiv:1506.08619.

Bambi, C., Modesto, L., Rachwal, L. (2017). Spacetime completeness of non-singular black holes in conformal gravity. JCAP 1705, 003. DOI:10.1088/1475-7516/2017/05/003. arXiv:1611.00865.

Calcagni, G., Modesto, L. (2017). Stability of Schwarzschild singularity in non-local gravity. Phys. Lett. B 773, 596. DOI:10.1016/j.physletb.2017.09.018. arXiv:1707.01119.

Myung, Y.S., Park, Y.J. (2018). Stability issues of black hole in non-local gravity. Phys. Lett. B 779, 342. DOI:10.1016/j.physletb.2018.02.023. arXiv:1711.06411.

As one can see by consulting these papers, it's not just a matter of providing arguments in favor or against singularity resolution. Many of these papers, in fact, do not take a side. But the do ask questions (partly answered there) that, as far as I know, remain open: 1) Are all singularities solved at the classical level or is the quantum theory necessary to eliminate some? 2) Is non-locality a sufficient mechanism to resolve singularity or are there other features (e.g., classical or quantum symmetries) that contribute?

GotAlight (talk) 15:09, 28 May 2018 (UTC)
 * I have added those papers, are there any more which you think are relevant/any more content you want to add? Absolutelypuremilk (talk) 12:37, 2 January 2019 (UTC)

Removal of singularities at non-linear level
these papers should also be added which show that there are no static and rotating singularities even at non-linear level: doi:10.1103/PhysRevD.98.064023, doi:10.1088/1475-7516/2018/06/014, doi:10.1103/PhysRevD.98.084041?. — Preceding unsigned comment added by 2001:981:29B1:1:F531:FCDE:342:5ED3 (talk) 04:50, 30 May 2019 (UTC)
 * I can't see where those papers show a non-singular metric which is a solution to the non-linear equations of motion? Absolutelypuremilk (talk) 13:29, 30 May 2019 (UTC)