A Unifying Theory of Dark Energy and Dark Matter: Negative Masses and
  Matter Creation within a Modified $\Lambda$CDM Framework
  Dark energy and dark matter constitute 95% of the observable Universe. Yet
the physical nature of these two phenomena remains a mystery. Einstein
suggested a long-forgotten solution: gravitationally repulsive negative masses,
which drive cosmic expansion and cannot coalesce into light-emitting
structures. However, contemporary cosmological results are derived upon the
reasonable assumption that the Universe only contains positive masses. By
reconsidering this assumption, I have constructed a toy model which suggests
that both dark phenomena can be unified into a single negative mass fluid. The
model is a modified $\Lambda$CDM cosmology, and indicates that
continuously-created negative masses can resemble the cosmological constant and
can flatten the rotation curves of galaxies. The model leads to a cyclic
universe with a time-variable Hubble parameter, potentially providing
compatibility with the current tension that is emerging in cosmological
measurements. In the first three-dimensional N-body simulations of negative
mass matter in the scientific literature, this exotic material naturally forms
haloes around galaxies that extend to several galactic radii. These haloes are
not cuspy. The proposed cosmological model is therefore able to predict the
observed distribution of dark matter in galaxies from first principles. The
model makes several testable predictions and seems to have the potential to be
consistent with observational evidence from distant supernovae, the cosmic
microwave background, and galaxy clusters. These findings may imply that
negative masses are a real and physical aspect of our Universe, or
alternatively may imply the existence of a superseding theory that in some
limit can be modelled by effective negative masses. Both cases lead to the
surprising conclusion that the compelling puzzle of the dark Universe may have
been due to a simple sign error.
