Comment on elastic proton scattering fromFe56in the giant resonance region ofCo57

In a recent publication, the rapid variation of the real part $\delta$ of the $J^{\pi }={\frac{5}{2}}^{+}$ phase shift for proton scattering from ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$ has been interpreted as the effect of the giant dipole resonance in ${}_{}{}^{57}{}_{}{}^{}\mathrm{Co}$ It is shown that the rapid variation of $\delta$ does not correspond to a rapid variation of the scattering amplitude of the $J^{\pi }={\frac{5}{2}}^{+}$ partial wave and thus does not indicate a resonance.