Nonstandard approach to gravity for the dark sector of the Universe

Understand

We summarize the present state of research on the darkon fuid as a model for the dark sector of the Universe.

• Nonrelativistic massless particles are introduced as a realization of the Galilei group in an enlarged phase space.
• The additional degrees of freedom allow for a nonstandard, minimal coupling to gravity respecting Einstein's equivalence principle.
• Extended to a self-gravitating fluid the Poisson equation for the gravitational potential contains a dynamically generated effective gravitational mass density of either sign.