AT1 - Extended Theories of Gravity and Quantum Cosmology |
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Speaker |
Hernandez, Xavier |
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Coauthors |
Hernandez, X.; Sussman, R. A.; Nasser, L. |
| Talk Title |
Approaching the Dark Sector through a bounding curvature criterion |
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Abstract |
Understanding the observations of dynamical tracers and the trajectories of lensed photons at galactic scales within the context of General Relativity (GR), requires the introduction of a hypothetical dark matter dominant component. The onset of these gravitational anomalies, where the Schwarzschild solution no longer describes observations, closely corresponds to regions where accelerations drop below the characteristic $a_{0}$ acceleration of MOND, which for systems of total baryonic mass $M$ occur at a mass-dependent radial distance, $R_{M}=(G M a_{0})^{1/2}$. At cosmological scales, inferred dynamics are also inconsistent with GR and the observed distribution of mass. The current accelerated expansion rate requires the introduction of a hypothetical dark energy dominant component. We here show that for a Schwarzschild metric at galactic scales, the scalar curvature, K, multiplied by the area function, both at the critical MOND transition radius, has an invariant value of $\kappa_{B}=K\times A=192\pi a_{0}^{2}/c^{4}$. For a FLRW metric, this same constant bounding curvature condition yields a covariant constraint which for a flat spacetime results in a cosmic expansion history which agrees with the $\Lambda$CDM concordance model for recent epochs, and which similarly tends to a de Sitter solution having a Hubble constant consistent with current inferred values. Thus, a simple purely geometric condition identifies the low acceleration regime of observed gravitational anomalies, and can be used to guide the development of modified gravity theories at both galactic and cosmological scales. |
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