identity

Synopsis:

template<Channel_t CH>
triqs_tprf::g2_iw_t identity (triqs_tprf::g2_iw_cvt g)

Two-particle response-function identity operator \(\mathbf{1}\)

Note

Assign to gf (g2_iw_t) yields move operation while assigning to gf_view (g2_iw_vt) causes extra copy operation

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

Return value

the unity operator \(\mathbf{1}\), in the given channel

Documentation

Constructs the unity-operator in the given channel

(1)\[\mathbf{1}_{abcd}(\omega,\nu,\nu') = \mathbf{1}_{\{\nu\alpha\beta\}, \{\nu'\gamma\delta\}}(\omega) \equiv \delta_{\nu\nu'} \delta_{\alpha\gamma} \delta_{\beta\delta}\]

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.