http://cds.cern.ch/record/538390/files/0202122.pdf

Neutrinos in cosmology

The Hubble expansion of galaxies, the 2.73 K black-body radiation background and the cosmic abundances of the light elements argue for a hot, dense origin of the universe - the standard big bang cosmology - and enable its evolution to be traced back fairly reliably to the nucleosynthesis era when the temperature was of O(1) MeV corresponding to an expansion age of O(1) s. All particles, known and hypothetical, would have been created at higher temperatures in the early universe and analyses of their possible effects on the abundances of the synthesized elements enable many interesting constraints to be obtained on particle properties. These arguments have usefully complemented laboratory experiments in guiding attempts to extend physics beyond the standard model, incorporating ideas such as supersymmetry, compositeness and unification. We first present a pedagogical account of relativistic cosmology and primordial nucleosynthesis, discussing both theoretical and observational aspects, and then proceed to examine such constraints in detail, in particular those pertaining to new massless particles and massive unstable particles. Finally, in a section aimed at particle physicists, we illustrate applications of such constraints to models of new physics.

https://iopscience.iop.org/article/10.1088/0034-4885/59/12/001/pdf

Big bang nucleosynthesis and physics beyond the standard model

With the observation of neutrino masses and mixings, the study of their electromagnetic interactions has assumed greater relevance both as verification of the $\ensuremath{\nu}$ standard model, and as a guide to new physics. After a standard description of massive neutrinos, this review assembles the present state of the art in the study of their electromagnetic interactions. Possible measurements of their static properties as test of new physics are described, a well as their behavior in strong magnetic fields. As such it should be helpful to both particle physicists and astrophysicists.

Neutrino electromagnetic interactions: A window to new physics

It is pointed out that the measurement of the deceleration parameter by Sandage (1972) implies an upper limit of a few tens of electron volts on the sum of the masses of all the possible light, stable particles that interact only weakly. In the discussion of the problem, it is assumed that the universe is expanding from an initially hot and condensed state as envisaged in the 'big-bang' theories.

An Upper Limit on the Neutrino Rest Mass

Non-GUT baryogenesis

On etudie la nucleosynthese dans l'univers avec des fluctuations de densite isothermes. Les neutrons, dans les regions de faible densite diffusent en retour vers des regions de densite elevee. Les abondances des elements legers sont donc contradictoires avec Ω B =1 si l'echelle des fluctuations de densite est aussi petite que 10 4 cm a T=1 MeV

/pdf/neutron-diffusion-and-nucleosynthesis-in-the-inhomogeneous-3bglieszcj.pdf

Neutron Diffusion and Nucleosynthesis in the Inhomogeneous Universe

Radiative decay of massive unstable neutrinos is examined in detail. Constraints on their mass and lifetime are established by solving the networks of nucleosynthesis and calculating the spectra of high-energy photons produced by massive neutrino decay. It is found that primordial nucleosynthesis sets stringent constraints on the mass and the lifetime of massive unstable neutrinos. According to these constraints together with constraints derived from other cosmological consideration and laboratory experiments, radiative decay of massive τ neutrinos is not allowed except for the case that the mass and the lifetime of the τ neutrino satisfy rather strict constraints; 30 MeV ≲ m ν τ ≲ 70 MeV, 10 2 s ≲ τ ντ ≲ 10 4 s. Constraints on neutrinos in the 4th generation are also derived.

Radiative Decay of Neutrino and Primordial Nucleosynthesis

Radiative decay of neutrino and primordial nucleosynthesis

We investigate nucleosynthesis in the universe with isothermal baryon density fluctuations taking into account nucleon diffusion during the nucleosynthesis. We find QB=l universe is marginally consistent with the light element abundances (D, 3He, 'He, 7Li) if the density contrast, R, is very high, ;C; 300 and the other parameters are tuned.

Nobuo Terasawa

Papers

Neutron Diffusion and Nucleosynthesis in the Inhomogeneous Universe

Radiative Decay of Neutrino and Primordial Nucleosynthesis

Radiative decay of neutrino and primordial nucleosynthesis

Nucleosynthesis in the Inhomogeneous Universe and Effects of Neutron Diffusion

Radiative decay of massive neutrinos and the photo-destruction of light elements