active-sterile mixing

Active-sterile mixing involves hypothetical particles called sterile neutrinos, which do not interact through the usual forces like regular (active) neutrinos do. However, they can mix with active neutrinos through quantum processes, meaning they can transform into each other. This mixing affects neutrino behavior, potentially impacting experiments and understanding of the universe, such as dark matter or early universe conditions. Essentially, it’s a way for the known neutrinos to "blend" with elusive sterile neutrinos, opening possibilities for new physics beyond current theories.