The “missing mass” problem is one of the fundamental puzzles in contemporary physics and astronomy. In recent years, attention has focused on modifications to the source side of Einstein’s equations of general relativity, the simplest of which is to add contributions to the energy-momentum tensor from heretofore unknown and unobserved degrees of freedom, i.e., dark matter. Inspired by gravitational thermodynamics, my collaborators and I have constructed* and studied** a phenomenological model of dark matter, which we call modified dark matter (MDM). For an accelerating Universe with positive cosmological constant (cc), such phenomenological considerations lead to the emergence of a critical acceleration parameter related to cc. Such a critical acceleration is an effective phenomenological manifestation of MDM, and it is found in correlations between dark matter and baryonic matter in galaxy rotation curves. The resulting MDM mass profiles, which are sensitive to cc, are consistent with observational data at both the galactic and cluster scales. In particular, the same critical acceleration appears both in the galactic and cluster data fits based on MDM. Furthermore, using some robust qualitative arguments, MDM appears to work well on cosmological scales, even though quantitative studies are still lacking. Surprisingly we have found*** certain non-local aspects of the quanta of modified dark matter, which may lead to novel non-particle phenomenology and which may explain why, so far, dark matter detection experiments have failed to detect dark matter particles.
* C.M. Ho et al., Phys. Lett. B693, 567 (2010).
** See our review article: D. Edmonds et al., Int. J. Mod. Phys. D27, 1830001 (2018).
*** C.M. Ho et al., Phys. Rev. D85, 104033 (2012).
Submitted by Y. J. Ng