triqs_tprf::identity
#include <tprf/linalg.hpp>
Synopsis
template<Channel_t CH>g2_iw_t identity (g2_iw_cvt g)
Two-particle response-function identity operator \(\mathbf{1}\)
Constructs the unity-operator in the given channel
\[\mathbf{1}_{abcd}(\omega,\nu,\nu') =
\mathbf{1}_{\{\nu\alpha\beta\}, \{\nu'\gamma\delta\}}(\omega)
\equiv
\delta_{\nu\nu'} \delta_{\alpha\gamma} \delta_{\beta\delta}\]
where the mapping of target-space indices \(\{a, b, c, d \}\) to \(\{\alpha, \beta\}, \{\gamma, \delta\}\) is channel dependent.
Storage is allocated and the result is returned by value.
Template parameters
CH selects the two-particle channel
Parameters
A two-particle response function \(A \equiv A_{abcd}(\omega, \nu, \nu')\) determinig the shape and size of the unity operator
Returns
the unity operator \(\mathbf{1}\), in the given channel