It is an established fact that the Standard Model has to be extended to explain the so-called Beyond the Standard Model (BSM) phenomena: dark matter, matter-antimatter asymmetry of the Universe and... Show moreIt is an established fact that the Standard Model has to be extended to explain the so-called Beyond the Standard Model (BSM) phenomena: dark matter, matter-antimatter asymmetry of the Universe and neutrino flavour oscillations. The difficulty of direct detection of new particles lies in the huge parameter space of the possible candidates. Hence, data coming from the cosmological and astrophysical observations provide invaluable directions for laboratory experiments.In this thesis we explore two methods of constraining new-physics candidates: through their influence on the primordial nucleosynthesis and through observable differences in the matter distribution caused by free-streaming of the dark-matter particles. We concentrate on the well-motivated extension of the SM that aims at explaining all 3 BSM problems at the same time: the Neutrino Minimal Standard Model. In this extension, there are 3 additional heavy neutral leptons, one of which plays the role of dark matter, while the other two are necessary for induction of matter-antimatter asymmetry and neutrino oscillations. The dark-matter candidate is an example of a Warm Dark Matter particle, the free-streaming of which might be detected in the Lyman-α forest spectra of distant quasars. The other two particles have lifetimes that make them relevant to the primordial nucleosynthesis. Show less
