The prediction for ${\mathrm{\alpha }}_{\mathit{s}}$ in the minimal supersymmetric SU(5) grand unified theory is generically subject to uncertainties arising from a gravitationally induced dimension-five operator. Unless the coefficient of this operator is small, the correlation between ${\mathrm{\alpha }}_{\mathit{s}}$ and the mass scale which governs proton decay to Kν is destroyed. Furthermore, a reduction of the experimental uncertainty in ${\mathrm{\alpha }}_{\mathit{s}}$ would not provide a significant test of the theory.

• Received 20 October 1992

DOI:https://doi.org/10.1103/PhysRevLett.70.2673