Name: V. Shtabovenko (email_not_shown)
Date: 11/19/17-02:06:09 PM Z


Hi,

sorry for the late reply. SetMandelstam can do this

?SetMandelstam

SetMandelstam[x, {p1, p2, p3, p4, p5}, {m1, m2, m3, m4, m5}] defines \
x[i, j] = (pi+pj)^2 and sets the pi on-shell. The pi satisfy: p1 + p2 \
+ p3 + p4 + p5 = 0.

SetMandelstam[x, {p1, p2, p3, p4, p5}, {m1, m2, m3, m4, m5}];
SP[p1 + p2] // ExpandScalarProduct
SP[p1 + p5] // ExpandScalarProduct

Cheers,
Vladyslav

Am 15.11.2017 um 19:59 schrieb Francesco:
> Hello,
> I need to compute a 2->4 amplitude within a model I created.
> In order to simplify the expression for the amplitude, is there a way to use the generalised Mandelstam variables like
> s_{i1i2..i4}=(p_i1+...+p_i4)^2
> and the others possible combinations?
>
> thanks
>



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