While the cosmic baryon asymmetry has been measured at high accuracy to be 6.1 \times 10 ^ { -10 } , a corresponding lepton asymmetry could be as large as 10 ^ { -2 } if it hides in the neutrino sector .
It has been known for some time that such an asymmetry could be generated from a small initial asymmetry given the existence of a sterile neutrino with a mass less than the mass of the active neutrino .
While the magnitude of the final lepton asymmetry is deterministic , its sign has been conjectured to be chaotic in nature .
This has been proven in the single momentum approximation , also known as the quantum rate equations , but has up to now not been established using the full momentum dependent quantum kinetic equations .
Here we investigate this problem by solving the quantum kinetic equations for a system of 1 active and 1 sterile neutrino on an adaptive grid .
We show that by increasing the resolution , oscillations in the lepton asymmetry can be eliminated so the sign of the final lepton asymmetry is in fact deterministic .
This paper also serves as a launch paper for the adaptive solver LASAGNA which is available at http : //users-phys.au.dk/steen .