One of the results of the visit of Prof. Dmitri D. Ryutov to Mainz in the summer of 2017 is a paper (co-authored by Profs. D. Budker and V. V. Flambaum) on a possible influence of a finite mass of the photon on galactic rotation curves. The leading current explanation of the anomalous stellar velocities is the presence of galactic halos formed by dark matter. This work points towards another possibility.
https://arxiv.org/abs/1708.09514
Press release about related results (in German): https://idw-online.de/de/news710200
Press release about related results (in English): https://www.alphagalileo.org/en-gb/Item-Display/ItemId/176042?returnurl=https://www.alphagalileo.org/en-gb/Item-Display/ItemId/176042