Year: 2006
Type: article
Abstract: The thermal leptogenesis in brane world cosmology is studied. In brane world cosmology, the expansion law is modified from the four-dimensional standard cosmological one at high temperature regime in the early universe. As a result, the well-known upper bound on the lightest light neutrino mass induced by the condition for the out-of-equilibrium decay of the lightest heavy neutrino, ${\stackrel{\texttildelow{}}{m}}_{1}\ensuremath{\lesssim}{10}^{\ensuremath{-}3}\text{ }\text{ }\mathrm{eV}$, can be moderated to be ${\stackrel{\texttildelow{}}{m}}_{1}\ensuremath{\lesssim}{10}^{\ensuremath{-}3}\text{ }\text{ }\mathrm{eV}\ifmmode\times\else\texttimes\fi{}({M}_{1}/{T}_{t}{)}^{2}$ in the case of ${T}_{t}\ensuremath{\le}{M}_{1}$ with the lightest heavy neutrino mass (${M}_{1}$) and the ``transition temperature'' (${T}_{t}$), at which the modified expansion law in brane world cosmology is smoothly connecting with the standard one. This implies that the degenerate mass spectrum of the light neutrinos can be consistent with the thermal leptogenesis scenario. Furthermore, as recently pointed out, the gravitino problem in supersymmetric case can be solved if the transition temperature is low enough ${T}_{t}\ensuremath{\lesssim}{10}^{6--7}\text{ }\text{ }\mathrm{GeV}$. Therefore, even in the supersymmetric case, thermal leptogenesis scenario can be successfully realized in brane world cosmology.
Authors: Nobuchika Okada, Osamu Seto
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2095557664