TrickMandelstam

Description

TrickMandelstam[expr, {s, t, u, (Subscript[m, 1]^2) + (Subscript[m, 2]^2)+ (Subscript[m, 3]^2)+ (Subscript[m, 4]^2)}] simplifies all sums in expr so that one of the Mandelstam variables s, t or u is eliminated by the relation s + t + u = (Subscript[m, 1]^2) + (Subscript[m, 2]^2)+ (Subscript[m, 3]^2)+ (Subscript[m, 4]^2) . The trick is that the resulting sum has the most short number of terms.

Examples

TrickMandelstam[(s + t - u) (2  (Subscript[M, W]^2) - t - u), {s, t, u, 
          2  (Subscript[M, W]^2)}] // Factor2

TrickMandelstam[
      M^2 s  -  s^2  +  M^2 t  -  s  t  +  M^2 u  -  s  u,  {s, 
        t, u, 2  M^2}]