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Abstract

Via gravitational closure [Dü+18]; [Wol22]; [Due20]; [Wie18] could show, how gravitational theories based on the matter content of spacetime can be systematically constructed. While this successfully reproduces general relativity for metric spacetimes, finding a solution for the simplest generalization of Maxwell electrodynamics with a vacuum birefringence allowing, area-metric structure has in general not been possible so far. For highly symmetric FLRW spacetimes a metric, as well as an area-metric solution could be derived [Due20]; [Fis17]. Based on this result, the constructive gravity program will be applied for spherically symmetric, stationary metric spacetimes. Furthermore, an according ansatz is worked out for area-metric geometries, and it is discussed which difficulties arise in finding a corresponding solution. Furthermore, the Etherington-duality is violated in the case of weakly area-metric gravitation [Sch+17]; [Ale20b]; [SW17], and this violation will be investigated with weak gravitational lensing experiments. The observable is the surface brightness, which is, however, heavily influenced by astrophysical processes like physical interaction of galaxies with tidal fields. Beyond that, it is studied how galaxies also get bent due to tidal interactions and how strong this effect is compared to its analog in gravitational lensing.