11 \({\psi_{e}}^{+}\left(\mathbf{\varepsilon}\right)=\frac{1}{2}k_{n}{\left\langle\text{tr}(\mathbf{\varepsilon})\right\rangle^{2}}_{+}+\mu\left(\mathbf{\varepsilon}_{\text{dev}}:\mathbf{\varepsilon}_{\text{dev}}\right)\ ,\)
12 \({\psi_{e}}^{-}\left(\mathbf{\varepsilon}\right)=\frac{1}{2}k_{n}{\left\langle\text{tr}(\mathbf{\varepsilon})\right\rangle^{2}}_{-}\ ,\)