![[Graphics:Images/index_gr_1.gif]](Images/index_gr_1.gif)
FermionSpinSum[x] constructs the Traces out of squared ampliudes.
See also: ComplexConjugate, DiracTrace, Tr.
![[Graphics:Images/index_gr_2.gif]](Images/index_gr_2.gif)
![[Graphics:Images/index_gr_3.gif]](Images/index_gr_3.gif)
Notice that SpinorUBar and SpinorU are only input functions. Internally they are converted to Spinor objects.
![[Graphics:Images/index_gr_4.gif]](Images/index_gr_4.gif){kind=small}
![[Graphics:Images/index_gr_5.gif]](Images/index_gr_5.gif)
![[Graphics:Images/index_gr_6.gif]](Images/index_gr_6.gif){kind=small}
![[Graphics:Images/index_gr_7.gif]](Images/index_gr_7.gif)
![[Graphics:Images/index_gr_8.gif]](Images/index_gr_8.gif){kind=small}
![[Graphics:Images/index_gr_9.gif]](Images/index_gr_9.gif)
![[Graphics:Images/index_gr_10.gif]](Images/index_gr_10.gif){kind=small}
![[Graphics:Images/index_gr_11.gif]](Images/index_gr_11.gif)
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