Traceless scalar tidal gravity: fixed lensing–to–dynamics ratio, luminal tensor waves, and acceleration screening
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2025
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| author | Vorel, Jan |
| author_facet | Vorel, Jan |
| contents | <p>We study a minimal modification of general relativity in which the trace equation is fixed to its general-relativistic form, while departures enter only through the traceless (tidal) sector via a scalar field. In the weak-field, quasi-static regime the two Newtonian-gauge potentials obey Poisson equations with fixed scalar coefficients, implying a parameter-independent relation between scalar-induced lensing and nonrelativistic dynamics. In any patch where the effective coupling is approximately constant, the scalar contribution to the Weyl (lensing) potential is exactly 3/4 of its contribution to the dynamical potential. On the luminal tensor branch, the principal part of the transverse–traceless wave equation is unchanged, so free gravitational waves propagate at the speed of light. We adopt a covariant acceleration-based screening ansatz, α→αeff(χ) = α/(1 + χn) with χ= a/ascr, which preserves the 3/4 imprint while suppressing slip in high-acceleration environments. Using the Cassini bound on the PPN parameter γPPN we obtain a sufficient Solar-System screening requirement αeff ≲10−4 and an operational screening-radius gate rscr,⊙ ≳100 AU, corresponding to ascr ≲6×10−7 m s−2. We propose a direct discriminator based on the excess lensing-to-dynamics ratio Rexcess ≡(Mlens−Mb)/(Mdyn−Mb) in galaxies and clusters, which approaches 3/4 when the scalar contribution dominates the excess and screening is weak.</p> |
| format | Recurso digital |
| id | zenodo_https___doi_org_10_5281_zenodo_18053041 |
| institution | Zenodo |
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| publishDate | 2025 |
| publisher | Zenodo |
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| spellingShingle | Traceless scalar tidal gravity: fixed lensing–to–dynamics ratio, luminal tensor waves, and acceleration screening Vorel, Jan Modified gravity general relativity traceless stress / traceless modification tidal gravity gravitational slip Weyl potential gravitational lensing galaxy clusters galaxy rotation curves screening mechanism post-Newtonian parameter gamma weak-field limit quasi-static limit dark matter phenomenology effective field theory (gravity) <p>We study a minimal modification of general relativity in which the trace equation is fixed to its general-relativistic form, while departures enter only through the traceless (tidal) sector via a scalar field. In the weak-field, quasi-static regime the two Newtonian-gauge potentials obey Poisson equations with fixed scalar coefficients, implying a parameter-independent relation between scalar-induced lensing and nonrelativistic dynamics. In any patch where the effective coupling is approximately constant, the scalar contribution to the Weyl (lensing) potential is exactly 3/4 of its contribution to the dynamical potential. On the luminal tensor branch, the principal part of the transverse–traceless wave equation is unchanged, so free gravitational waves propagate at the speed of light. We adopt a covariant acceleration-based screening ansatz, α→αeff(χ) = α/(1 + χn) with χ= a/ascr, which preserves the 3/4 imprint while suppressing slip in high-acceleration environments. Using the Cassini bound on the PPN parameter γPPN we obtain a sufficient Solar-System screening requirement αeff ≲10−4 and an operational screening-radius gate rscr,⊙ ≳100 AU, corresponding to ascr ≲6×10−7 m s−2. We propose a direct discriminator based on the excess lensing-to-dynamics ratio Rexcess ≡(Mlens−Mb)/(Mdyn−Mb) in galaxies and clusters, which approaches 3/4 when the scalar contribution dominates the excess and screening is weak.</p> |
| title | Traceless scalar tidal gravity: fixed lensing–to–dynamics ratio, luminal tensor waves, and acceleration screening |
| topic | Modified gravity general relativity traceless stress / traceless modification tidal gravity gravitational slip Weyl potential gravitational lensing galaxy clusters galaxy rotation curves screening mechanism post-Newtonian parameter gamma weak-field limit quasi-static limit dark matter phenomenology effective field theory (gravity) |
| url | https://doi.org/10.5281/zenodo.18053041 |