Galactic evolution of ~7Li

摘要

Lithium represents a key element in cosmology, as it is one of the few nuclei syn-thesized during the Big Bang. The primordial abundance of ~7Li allows us to impose constraints on the primordial nucleosynthesis and on the baryon density of the universe. However,~7Li is not only produced during the Big Bang but also during galactic evolution: measures of stellar Li in our Galaxy suggest an almost constant Li abundance (the so-called Spite plateau) at low metallicities and a subsequent increase in the disk stars, leading to a Li abundance in Population I stars higher by a factor of ten than in Population II stars. This means that there must exist several possible stellar sources of ~7Li: asymptotic giant branch stars, supernovae, novae, red giant stars. ~7Li is also partly produced in spallation processes while 6 Li is entirely produced by such processes. All of these sources have been included in galactic chemical evolution models and constraints have been derived on the primordial ~7Li and its evolution, as well on stellar models. I will review these models and their results and what we have learned about ~7Li evolu-tion. Some still open problems, such as the disagreement between the primordial ~7Li abundance as derived by WMAP and as measured in Population II stars, and the uncertainties about the main sources of stellar ~7Li will be discussed.