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Copy file name to clipboardExpand all lines: docs/src/appendix/symmetric_tutorial.md
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-`vertices::NTuple{L,T}`: list of fusion vertex labels of type `T` and length `L = N - 1`
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For our current application only `uncoupled` and `coupled` are relevant, since
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$\mathbb{Z}_2$ irreps are self-dual and have Abelian fusion rules, so that irreps on the inner lines of a fusion tree are completely determined by the uncoupled irreps. We will come back to
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these other properties when discussion more involved applications. Given some `TensorMap`,
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the method `TensorKit.fusiontrees(t::TensorMap)` returns an iterator over all pairs of
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splitting and fusion trees that label the subblocks of `t`.
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$\mathbb{Z}_2$ irreps are self-dual and have Abelian fusion rules, so that irreps on the
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inner lines of a fusion tree are completely determined by the uncoupled irreps. We will come
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back to these other properties when discussion more involved applications. Given some
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`TensorMap`, the method `TensorKit.fusiontrees(t::TensorMap)` returns an iterator over all
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pairs of splitting and fusion trees that label the subblocks of `t`.
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We can now put this into practice by directly constructing the $ZZ$ operator in the irrep
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basis as a $\mathbb{Z}_2$-symmetric `TensorMap`. We will do this in three steps:
@@ -544,12 +545,14 @@ It is then simple to check that this is indeed what we expect.
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!!! note
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From the construction of the Hamiltonian operators
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[in terms of creation and annihilation operators](bosonham) we clearly see that they are
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invariant under a transformation $a^\pm \to e^{\pm i\theta} a^\pm$. More generally, any
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invertible transformation on the auxiliary space leaves the resulting contraction unchanged.
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This ambiguity in the definition clearly shows that one should really always think in terms
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of the fully symmetric procucts of $a^+$ and $a^-$ rather than in terms of these operators
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themselves. In particular, one can always decompose such a symmetric product into the
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[form above](bosonham) by means of an SVD.
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invariant under a transformation $a^\pm \to e^{\pm i\theta} a^\pm$. More generally, for
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a two-site operator that is defined as the contraction of two one-site operators across
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an auxiliary space, modifying the one-site operators by applying transformations $Q$ and
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$Q^{-1}$ on their respective auxiliary spaces for any invertible $Q$ leaves the
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resulting contraction unchanged. This ambiguity in the definition clearly shows that one
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should really always think in terms of the fully symmetric procucts of $a^+$ and $a^-$
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rather than in terms of these operators themselves. In particular, one can always
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decompose such a symmetric product into the [form above](bosonham) by means of an SVD.
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