Comment on ‘‘testing’’ the Gamow-Teller sum rule

Several recent papers purport to ‘‘test’’ the Gamow-Teller sum rule. They compare the differences between incomplete strength function integrals for the ${\mathrm{\beta }}^{\mathrm{-}}$ and ${\mathrm{\beta }}^{+}$ directions with the quantity 3(N-Z) and interpret discrepancies as degrees of failure of the sum rule. We point out that the Gamow-Teller sum rule is an exact operator relationship, not a model to be tested. It is useful for determining whether a measured strength function is complete.