# scale -- reduces a list or divisor by the gcd of its coefficients

## Description

Let $D$ be an $S_n$ symmetric $Q$-divisor on $\bar{M}_{0,n}$. This function reduces a symmetric divisor $D$ by the gcd of its coefficients in the standard basis. This gives a canonical representative of each nonzero ray in $Pic(\bar{M}_{0,n})_Q^{S_n}$.

 i1 : D=symmetricDivisorM0nbar(6,288*B_2+144*B_3) o1 = 288*B + 144*B 2 3 o1 : S_6-symmetric divisor on M-0-6-bar i2 : scale(D) o2 = 2*B + B 2 3 o2 : S_6-symmetric divisor on M-0-6-bar

## Ways to use scale :

• "scale(SymmetricDivisorM0nbar)"

## For the programmer

The object scale is .