Constraints on the variations of fundamental couplings by stellar models .

The effect of variations of the fundamental constants on the thermonuclear rate of the triple alpha reaction, 4He(αα, γ)12C, that bridges the gap between 4He and 12C is investigated. We follow the evolution of 15 and 60 M zero metallicity stellar models, up to the end of core helium burning. They are assumed to be representative of the first, Population III stars which differ from later Pop I and II stars in their evolution due to the absence of initial CNO elements (zero metallicity). The calculated oxygen and carbon abundances resulting from helium burning can then be used to constrain the variations of the fundamental constants.