Testing disk instability models for giant planet formation

Disk instability is an attractive yet controversial means for the rapid formation of giant planets in our solar system and elsewhere. Recent concerns regarding the first adiabatic exponent of molecular hydrogen gas are addressed and shown not to lead to spurious clump formation in the author's disk instability models. A number of disk instability models have been calculated in order to further test the robustness of the mechanism, exploring the effects of changing the pressure equation of state, the vertical temperature profile, and other parameters affecting the temperature distribution. Possible reasons for differences in results obtained by other workers are discussed. Disk instability remains as a plausible formation mechanism for giant planets.