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Ariel Edery McGill It is shown that it is not possible in the absence of dark matter to construct a four-dimensional metric that can explain galactic observations. In particular, by working with an effective potential, it is shown that a metric which is constructed to fit flat rotation curves leads to the wrong sign for the bending of light i.e. repulsion instead of attraction. Hence, without dark matter galactic observations cannot be explained in terms of geodesic motion on a four-dimensional metric. This reveals a new bright side to dark matter : it is indispensable if we wish to retain the cherished equivalence principle.
Tuesday, April 6th 1999, 13:00 |