Graviton-photon oscillations in an expanding universe

Journal Article · 27 March 2024 · Physics of the Dark Universe

DOI: https://doi.org/10.1016/j.dark.2024.101480 · OSTI ID:2375415

Anninos, Peter ^[1]; Rothman, Tony  ^[2]; Palessandro, Andrea ^[3]

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1. Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
2. New York Univ. (NYU), NY (United States)
3. Deloitte Artificial Intelligence Institute (Denmark)

Through the Gertsenshtein effect, the presence of a large external B-field may allow photons and gravitons to mix in a way that resembles neutrino oscillations and is even more similar to axion-photon mixing. Assuming a background B-field (or any field that behaves like one), we examine the Gertsenshtein mechanism in the context of FLRW expanding universe models, as well as de Sitter space. The conformal invariance of Maxwell’s equations and the conformal noninvariance of the Einstein equations preclude the operation of the Gertsenshtein effect at all scales. In general we find for the matter- and radiation-dominated cases, graviton-oscillations are possible only at late conformal times or when the wavelengths are much shorter than the horizon (kn $$\gg$$ 1), but that the time-dependent oscillations eventually damp out in any case. Further, the presence of charged particles additionally damps out the oscillations. For the de Sitter universe, we find that oscillations are possible only at early conformal times (n $$\ll$$ H^-1) and for wavelengths short compared to the Hubble radius, but eventually freeze in when wavelengths become longer than the Hubble radius. In principle a Gertsenshtein-like mechanism might influence the balance of particle species in an inflationary phase before freezing in; however, we find that in all our models the mixing length is larger than the Hubble radius. We discuss several possible remedies to this situation.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 2375415
• Report Number(s): LLNL--JRNL-859129; 1089797
• Journal Information: Physics of the Dark Universe, Journal Name: Physics of the Dark Universe Journal Issue: 101480 Vol. 44; ISSN 2212-6864
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English