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TrickMandelstam

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Description

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

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Examples

Converted from the *Mathematica* notebook TrickMandelstam.nb