commutator()

std::tuple< STensor, std::array< SBasis, 2 > > syten::STensorImpl::commutator	(	STensorProxy	A,
		STensorProxy	B,
		ConstSpan< SBasis > const &	AIds,
		ConstSpan< SBasis > const &	BIds
	)

Calculates the commutation of tensors A and B with respect to the requested legs, i.e.

AB-BA. This works for any tensor ranks, but therefore needs to be handeled with care.

Parameters

A	is an STensor of arbitrary rank.
B	is an STensor of arbitrary rank.
AIds	specifies first the left leg of A than the right one.
BIds	specifies first the left leg of B than the right one.

Returns

The commutator and the new SBasisIds of the matrix legs.

Remarks

This function is not autodifferentiable.

References syten::STensorImpl::STensor::b(), project(), syten::STensorImpl::SBasis::repro(), syten::STensorImpl::SBasis::set_id(), syten::SpanImpl::ConstSpan< T >::size(), SYTEN_ASSERT, and SYTEN_ASSERT_DEBUG.

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