Complex mass means gravitational mass + i.lambda.higgs mass. The weak coupling constants are all proportional to (higgs) mass with Higgs vacuum value (=246 GeV) as the proportionality constant.
Thus mass necessarily becomes a complex number.
The real part produces attractive gravity forces and the imaginary part produces repulsive "weak" forces. The factor lambda regulates the relative strength and range of the weak force.
The weak force possibly acquires a long-range in company of the gravity force.
Mass must thus be written as m.exp(phi(x)).
Phase phi being function of x (with contravariant-indexes 0,1,2,3), this phase automatically creates/necessitates new gauge fields and intermediary bosons.
This prevents the singularity in the black hole.
The equivalence principle has not been tested in high density matter (nucleus, white dwarfs, neutron stars, black holes etc.) and below the atto-m ranges.
A complete description of causality is not possible without the inclusion of repulsive forces (and their geodesics) in General Relativity.
A complex mass leads to a complex energy momentum tensor and a complex metric. The complex metric can explain anti-particle trajectories (rotated or reversed geodesics).