Template Class OpMaker¶

Defined in File op.hpp

Class Documentation¶

template<Statistics S> class OpMaker¶

makes a tensor-level many-body operator

A many-body operator has the following generic form: $1 𝑃 𝑇 𝑘 1 𝑘 2 \dots 𝑘 𝐾 𝑏 1 𝑏 2 \dots 𝑏 𝐵 𝐴 𝑏 1 𝑏 2 \dots 𝑏 𝐵 𝑘 1 𝑘 2 \dots 𝑘 𝐾$ where ${𝐵, 𝐾}$ are number of bra/ket indices of $𝑇$ or, equivalently, the number of creators/annihilators of normal-ordered (w.r.t. the default vacuum) operator $𝐴$ . Hence ${𝑏 𝑖}$ / ${𝑘 𝑖}$ are (quasi)particle creation/annihilation indices. For example, for fermionic operators relative to Fermi vacuum these are:

(pure) excitation: (active) unoccupied/occupied, respectively;
(pure) deexcitation: occupied/unoccupied, respectively; For generic operators (neither excitation nor deexcitation) complete basis indices are assumed by default.

$𝑃$ is the “normalization” factor and depends on the vacuum used to define $𝐴$ , and indices ${𝑏 𝑖}$ / ${𝑘 𝑖}$ .

Note

The choice of computational basis can be controlled by the default Context. See SeQuant/core/context.hpp and SeQuant/mbpt/context.hpp

Warning

Tensor $𝑇$ will be antisymmetrized if get_default_context().spbasis() == SPBasis::spinorbital, else it will be particle-symmetric; the latter is only valid if # of bra and ket indices coincide.

Public Types

enum class UseDepIdx¶

Values:

enumerator Bra¶: bra/cre indices depend on ket

enumerator Ket¶: ket/ann indices depend on bra

enumerator None¶: use plain indices

Public Functions

template<typename IndexSpaceTypeRange1, typename IndexSpaceTypeRange2> inline OpMaker(OpType op, const cre<IndexSpaceTypeRange1> &cre_list, const ann<IndexSpaceTypeRange2> &ann_list)¶

Parameters:

op – [in] the operator type
cre_list – [in] list of creator indices
ann_list – [in] list of annihilator indices

OpMaker(OpType op, ncre nc, nann na)¶

Parameters:

op – [in] the operator type
nc – [in] number of bra indices/creators
na – [in] number of ket indices/annihilators

OpMaker(OpType op, std::size_t rank)¶

creates a particle-conserving replacement operator

Parameters:

op – [in] the operator type
rank – [in] particle rank of the operator (# of creators = # of annihilators = rank )

OpMaker(OpType op, ncre nc, nann na, const cre<IndexSpace> &cre_space, const ann<IndexSpace> &ann_space)¶

Parameters:

op – [in] the operator type
nc – [in] number of bra indices/creators
na – [in] number of ket indices/annihilators
cre_space – [in] IndexSpace referred to be the creator
ann_space – [in] IndexSpace referred to be the annihilators

ExprPtr operator()(std::optional<UseDepIdx> dep_opt = {}, std::optional<Symmetry> opsymm_opt = {}) const¶

Parameters:

dep_opt – [in] if given, controls whether bra (*dep_opt == UseDepIdx::Bra) / ket (*dep_opt == UseDepIdx::Ket) indices are dependent on the, respectively, ket/bra indices (i.e., use them as protoindices); if (*dep_opt == UseDepIdx::None) then plain indices are used; if dep_opt is not given then the default is determined by the MBPT context.
opsymm_opt – [in] if given, controls whether (anti)symmetric tensor is returned; if opsymm_opt is not given then the default is determined by the MBPT context.

Public Static Functions

template<typename TensorGenerator> static inline ExprPtr make(const container::svector<IndexSpace> &creators, const container::svector<IndexSpace> &annihilators, TensorGenerator &&tensor_generator, UseDepIdx dep = UseDepIdx::None)¶

Template Parameters:

TensorGenerator – callable with signature TensorGenerator(range<Index>, range<Index>, Symmetry) that returns a Tensor with the respective bra/cre and ket/ann indices and of the given symmetry

Parameters:

creators – [in] creator indices
annihilators – [in] annihilator indices
tensor_generator – [in] the callable that generates the tensor
dep – [in] whether to use dependent indices

template<typename TensorGenerator> static inline ExprPtr make(std::initializer_list<IndexSpace::Type> creators, std::initializer_list<IndexSpace::Type> annihilators, TensorGenerator &&tensor_generator, UseDepIdx csv = UseDepIdx::None)¶

Protected Functions

OpMaker(OpType op)¶

inline const auto ncreators() const¶

inline const auto nannihilators() const¶

Protected Attributes

OpType op_¶

container::svector<IndexSpace> cre_spaces_¶

container::svector<IndexSpace> ann_spaces_¶