Semi-analytic theories are important tools to investigate various conditions in the Universe, while supercomputer simualtions require significant computing time and cannot cover a full range of possible conditions.

I developed a semi-analyticl theory that can calculate time evolution of molecular cloud mass functions. I also proposed a scenario of our Solar system formation, where protosolar system was embedded in a structure called filament and this filament was impacted by a shock wave from a nearby supernova. By comparing these with observations, we can constrain the evolutionary timescale of molecular clouds and the formation condition of our Solar system.