Question about simplfying algebraic expressions within FORM

[williamronayne-byte]

Hello,
I am trying to do some tensor calculations in FORM in order to calculate projectors for tensor products of representations. I have inputted some properties of the tensors as substitution rules, for example:

id d3(i?, s?, t?) * d3(j?, s?, t?) = ((N-1)/(N+1)) * d2(i, j);
id d3(i?,j?,s?)*d3(s?,ip?,jp?) = d4(i,j,ip,jp) - (N+1)^-1*d2(i,j)*d2(ip,jp);

I am trying to do things like check a Projector P satisfies P^2 = P. For example:

Local test5 =  Pvts3(i,j,k,s,t,u)*Pvts3(s,t,u,ip,jp,kp) - Pvts3(i,j,k,ip,jp,kp);
id Pvts3(i?,j?,k?,ip?,jp?,kp?) = (N+1)*(N-1)^-1*(d4(i,j,ip,jp)-(N+1)^-1*d2(i,j)*d2(ip,jp))*d2(k,kp);

The above would output zero if the projector satisfies P^2 = 1

Due to the presence of fractions like (N+1)^-1 in the identities for the tensors, FORM isn't simplifying any of the algebra as it doesn't automatically know how to add fractions together. I am currently having to copy and paste expressions into Mathematica and simplify there.

Does anyone know of a way to get FORM to simplify the algebra?
Would I just need to specify every possible expression involving the addition of fractions as a substitution rule?

Many thanks for any help.

[jodavies]

Here you are looking for polyratfun: https://form-dev.github.io/form-docs/master/manual/#SECTION0081140000000000000000

You can either use this directly in your id statements, or move N into it, and use the Denominators statement to pick those up in a way you can move in.