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## MpWignerEckartThe ## Synopsis
## Options
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`--force` overwrite the output file, if it exists
## DescriptionThe If the output file already exists, then The To find out the symmetry list of an existing wavefunction, use ## Examples- Project an {$SU(2)$} symmetric spin chain to {$U(1)$}.
`mp-wigner-eckart "Sz:U(1)" psi1 psi2` If`psi2` already exists, then this will fail with an error, leaving the existing file`psi2` untouched. To force overwriting`psi2` , add the`-f` option.
## RestrictionsThere are some limitations in the implementation of - If the wavefunction has more than one {$SU(2)$} symmetry, then unfortunately it isn't possible to project just one {$SU(2)$} symmetry, all of them need to be projected at the same time.
- The only projection that is currently implemented is {$SU(2) \supset U(1)$}. In the future it is hoped to generalize this to other projections, such as {$SU(2) \supset D_\infty \supset U(1)$}, and {$SU(2) \supset Z_3$}, and {$SU(2) \supset D_\infty \supset Z_2$}.
## NotesThis command gets its name from the Wigner-Eckart theorem, which is the basic theorem that underlies the concept of non-abelian MPS. |

Page last modified on July 25, 2016, at 07:41 PM