Modified gravity at large scales on quantum spacetime in the IKKT model

The gravitational dynamics of 3+1 dimensional covariant quantum spacetime in the IKKT or IIB matrix model is studied at one loop, combining the Yang-Mills-type matrix action with the induced Einstein-Hilbert action. This combined action leads to interesting modifications of the gravitational dynamics at long distances, governed by modified Einstein equations including an extra geometrical tensor interpreted as ‘‘mirage matter’’. In particular we find extra non-Ricci flat geometric modes with a non-standard dispersion relation, with features reminiscent of dark matter.