FeynCalc manual (development version)

TrickMandelstam

TrickMandelstam[expr, {s, t, u, m1^2 + m2^2 + m3^2 + m4^2}] simplifies all sums in expr so that one of the Mandelstam variables ss, tt or uu is eliminated by the relation s+t+u=m12+m22+m32+m42s + t + u = m_1^2 + m_2^2 + m_3^2 + m_4^2 . The trick is that the resulting sum has the most short number of terms.

See also

Overview, SetMandelstam.

Examples

ClearAll[s, t, u] 
 
(s + t - u) (2 SMP["m_W"]^2 - t - u) 
 
TrickMandelstam[%, {s, t, u, 2 SMP["m_W"]^2}] // Factor2

(s+tu)(2mW2tu)(s+t-u) \left(2 m_W^2-t-u\right)

2s(umW2)-2 s \left(u-m_W^2\right)

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

M2s+M2t+M2us2stsuM^2 s+M^2 t+M^2 u-s^2-s t-s u

2M2(M2s)2 M^2 \left(M^2-s\right)