In general, a positive <math>\Lambda</math> causes acceleration to the universe expansion, whereas negative <math>\Lambda</math> and ordinary matter tend to decelerate it.<ref name="CSR"/> When the ''Supernova Cosmology Project Collaboration'' and ''High-Z Supernova Team Collaboration'' started their research at the beginning of 1990s, both prevailing mainstream cosmological models assumed decelerating universe scenarios. The processing of collected data from research observations however indicated that the universe is accelerating and requires something like non-zero cosmological constant.<ref name="RiessNobel">{{cite web | In general, a positive <math>\Lambda</math> causes acceleration to the universe expansion, whereas negative <math>\Lambda</math> and ordinary matter tend to decelerate it.<ref name="CSR"/> When the ''Supernova Cosmology Project Collaboration'' and ''High-Z Supernova Team Collaboration'' started their research at the beginning of 1990s, both prevailing mainstream cosmological models assumed decelerating universe scenarios. The processing of collected data from research observations however indicated that the universe is accelerating and requires something like non-zero cosmological constant.<ref name="RiessNobel">{{cite web |