We know that while propagating through space, neutrinos changes their identities continuously.i.e., they oscillate from one flavour to another while travelling. This phenomenon suggest that neutrinos do feel time and therefore must be massive.

My question is that what will possibily happen if we decrease the background temperature to near absolute zero or increase it to thousands of kalvins? Is there any known tool for handling such situations?

(My current knowledge of neutrino oscillations is limited to vacuum case only. I will learn oscillations in matter in near future.)