     \delta\Theta_{{\bf k},{\bf q}}(\lambda,\Delta\lambda)   }{     \varepsilon_{\bf k} - \varepsilon_{({\bf k}+{\bf q})} + \omega_{\bf q}   }   \left\{         g_{\bf q} \,      c_{{\bf k},\sigma}^{\dagger} c_{({\bf k}+{\bf q}),\sigma}      b_{\bf q}^{\dagger}     