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Inspired by the post Re: the physics package I decided to have a closer look at the function FeynmanDiagrams. As the Lagrangian I thought I might as well take the QED Lagrangian for a massless spinor field Q[i](X) coupled to an external electromagnetic field A[mu](X): 
restart:
with(Physics):
Setup(advanced):
L_QED :=
   +Dagger(Q[i](X)) * Dgamma[4] * Dgamma[mu][i,j] * I * diff(Q[j](X),X[mu])
   +Dagger(Q[i](X)) * Dgamma[4] * Dgamma[mu][i,j] * e * A[mu](X) * (Q[j](X));
Even though this expression may seem a bit daunting, it does not get very much simpler in the Standard Model of particle physics. However, when I try something like 
FeynmanDiagrams(L_QED, points = [[X,Y]], fields = {A, Q});
I get an error saying that
Error, (in FeynmanDiagrams) unable to handle objects like Dagger(Q[i](x1, x2, x3, x4)) inside products
Writing the Dagger(Q[i](X)) terms instead as Dagger(Q[i])(X) or as Dagger(Q)[i](X) (clearly I am catching at straws here) helps nothing as they produce their own (almost identical) errors:
Error, (in FeynmanDiagrams) found more than 1 noncommutative object in the commutative product: Physics:-`*`(A[mu](x1, x2, x3, x4), Q[j](x1, x2, x3, x4))*Physics:-`*`(Physics:-Dgamma[mu][i, j], e, (Dagger(Q[i]))(x1, x2, x3, x4), Physics:-Dgamma[4])
and
Error, (in FeynmanDiagrams) found more than 1 noncommutative object in the commutative product: Physics:-`*`(A[mu](x1, x2, x3, x4), Q[j](x1, x2, x3, x4))*Physics:-`*`(Physics:-Dgamma[mu][i, j], e, Dagger(Q)[i](x1, x2, x3, x4), Physics:-Dgamma[4])
respectively. Go figure! I am lost, and, to be honest, I am frustrated over the seemingly impenetrable Physics environment of Maple 11.
error package

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