The complexity factor, originally based on a probabilistic description of a physical system, was re-defined by Herrera et al. for relativistic systems. This involves an assessment of the energy density inhomogeneity, anisotropic and shear stresses, and in the case of radiating collapse, the effects of heat flux. Already well integrated into the modelling of static configurations, the complexity factor is now being studied with respect to dynamical, self-gravitating systems. For static systems, the constraint of vanishing complexity is typically used however for the non-static case, the physical viability of the vanishing condition is less clear. To this end, we consider the ideal case of vanishing complexity in order to solve for the time-dependent gravitational potentials and generate models. We find that vanishing complexity constrains the metric to be of a form similar to that of Maiti’s conformally flat metric.

We investigate the surface tension of strange quark stars by making use of a color-flavor-locked (CFL) equation of state. Compact objects with anisotropic pressures provide richer systems for studying surface tension variations, and establishing physically viable ranges of parameters in maintaining hydrostatic equilibrium of quark matter at densities exceeding that of nuclear material. The strange quark mass, the QCD gap energy, and the MIT bag constant are key parameters in the CFL equation of state used, and thus feature in calculations of the surface tension.