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Reconstructing the graviton
by Alfio Bonanno, Tobias Denz, Jan M. Pawlowski, Manuel Reichert
This is not the latest submitted version.
Submission summary
| Authors (as registered SciPost users): | Jan M. Pawlowski · Manuel Reichert |
| Submission information | |
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| Preprint Link: | https://arxiv.org/abs/2102.02217v2 (pdf) |
| Date submitted: | July 29, 2021, 4:32 p.m. |
| Submitted by: | Manuel Reichert |
| Submitted to: | SciPost Physics |
| Ontological classification | |
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| Academic field: | Physics |
| Specialties: |
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| Approach: | Theoretical |
Abstract
We reconstruct the Lorentzian graviton propagator in asymptotically safe quantum gravity from Euclidean data. The reconstruction is applied to both the dynamical fluctuation graviton and the background graviton propagator. We prove that the spectral function of the latter necessarily has negative parts similar to, and for the same reasons, as the gluon spectral function. In turn, the spectral function of the dynamical graviton is positive. We argue that the latter enters cross sections and other observables in asymptotically safe quantum gravity. Hence, its positivity may hint at the unitarity of asymptotically safe quantum gravity.
Current status:
Reports on this Submission
Report #2 by Anonymous (Referee 2) on 2021-8-25 (Invited Report)
- Cite as: Anonymous, Report on arXiv:2102.02217v2, delivered 2021-08-25, doi: 10.21468/SciPost.Report.3441
Report
Report #1 by Anonymous (Referee 1) on 2021-8-9 (Invited Report)
- Cite as: Anonymous, Report on arXiv:2102.02217v2, delivered 2021-08-09, doi: 10.21468/SciPost.Report.3359
Report
If the above concern is addressed adequately, I would be happy to recommend the paper for publication.
As a final minor point, following up on the question of numerically accessible Lorentzian formulations, it seems that there are some new developments in the field of spin foams, see [2104.00485]. I leave it to the authors whether they want to include a reference to this.
We apologise for the confusion regarding the computation of the background spectral function. In the previous version of this work, we had treated the low momentum dependence only numerically, which lead to an oversight of a contribution to the log-like divergence. In the present version, we computed the log-like IR contributions analytically (c.f. the computation of $A_{\bar g}$), which allowed us to improve the numerics in the IR. This has resulted in a slightly simpler background spectral function (a smaller number of Breit-Wigner structures in Table 2) and a smaller error in the reconstruction ($E_\text{rel} < 10^{-3}$ vs $E_\text{rel} < 10^{-2}$ before). The only remarkable change in the background spectral function is that it now starts negative in the deep IR, otherwise all features remained qualitatively the same. The different choice of parameters $\Delta\Gamma_{1,2}$ has no impact on the reconstruction.
We hope that this clears up the referee's concern. We also thank the referee for bringing the reference to our attention, which we will cite in the next version of our work.
Author: Manuel Reichert on 2021-10-06 [id 1815]
(in reply to Report 2 on 2021-08-25)We thank the referee for pointing out the reference error, which we have corrected. We carefully checked the manuscript for further minor mistakes.