Abstract
We develop the framework for testing Lorentz invariance in the dark matter sector using galactic dynamics. We consider a Lorentz violating (LV) vector field acting on the dark matter component of a satellite galaxy orbiting in a host halo. We introduce a numerical model for the dynamics of satellites in a galactic halo and for a galaxy in a rich cluster to explore observational consequences of such an LV field. The orbital motion of a satellite excites a time dependent LV force which greatly affects its internal dynamics. Our analysis points out key observational signatures which serve as probes of LV forces. These include modifications to the line of sight velocity dispersion, mass profiles and shapes of satellites. With future data and a more detailed modeling these signatures can be exploited to constrain a new region of the parameter space describing the LV in the dark matter sector.
Highlights
ArXiv ePrint: 1702.07726 on these interactions are very strong for SM particles [4]
To obtain an order of magnitude estimate of the strength of the Lorentz violating (LV) effects, we compare the time dependent part of the LV force with the standard gravitational interactions, namely the gravitational force generated by the satellite halo itself and the tidal effects produced by the gravitational field of the host halo
We have performed a preliminary investigation of the dynamics of galactic satellites in the presence of a LV force in the DM sector
Summary
We will assume that the Universe is endowed with a preferred time direction or foliation of space-time that breaks Lorentz invariance This can be described by introducing the ‘Aether’ vector U μ and forcing it to have a time-like unit norm that selects the preferred time direction. The Solar System bounds can be satisfied by specific combinations of the couplings, which still yield part of the parameter space totally unconstrained The latter can be explored through other observations, as Big Bang Nucleosynthesis (BBN) [32], dynamics of binary systems [20, 21], or linear cosmology [25]. We equip the Æ theory with an explicit coupling between the LV vector and DM which will break the Lorentz invariance of this component This is achieved by modifying the action for a DM particle as follows [24]. The sum of the two actions (2.1) and (2.3), plus any other minimally coupled matter species, defines the LVDM model whose small scales dynamics will be investigated
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