The ft-values of the mirror nuclei and the axial-vector coupling constant

We updated the ft-values of the mirror nuclei with A ≤ 43, using all relevant experimental data as well as the recent progress in the theory of 'outer' radiative corrections of order Zα2 and of order Z2α3. The new ft-values are combined with three different sets of Gamow-Teller matrix elements to deduce information on the quenching of the axial-vector coupling constant. In all three cases this results in a value for gA/gV which is surprisingly close to 1.00, while possible evidence is found for a small mass-number dependence of the quenching