I'm having trouble with a simple replacement-rule. It seems my understanding of Blanks is wrong. I have an expression containing the following multiple times:
e[a1,a2] e[b1,b2] e[c1,c2]
I want to replace this expression with zero, whenever
a2=b2=c2. The following replacement-rule however does nothing to the expression:
e[a1,1] e[b1,1] e[c1,1]/.e[_,a_] e[_,a_] e[_,a_]->0,
whereas the following works:
e[a1,1] e[b1,1] e[c1,1]/.e[_,a_] e[d_,a_] e[f_,a_]->0
I don't really understand why. I know that
Pattern, which is why it is colored green in the rule, whereas
_ has the
Blank and is left in black. But that doesn't really help me.
Any help is appreciated!