Function: ellglobalred
Section: elliptic_curves
C-Name: ellglobalred
Prototype: G
Help: ellglobalred(E): E being an elliptic curve, returns [N,[u,r,s,t],c],
 where N is the conductor of E, [u,r,s,t] leads to the standard model for E,
 and c is the product of the local Tamagawa numbers c_p.
Description:
 (gen):gen        ellglobalred($1)
Doc:
 calculates the arithmetic conductor, the global
 minimal model of $E$ and the global \idx{Tamagawa number} $c$.
 $E$ must be a \var{smallell} as output by \kbd{ellinit}, \emph{and is supposed
 to have all its coefficients $a_i$ in} $\Q$. The result is a 3 component
 vector $[N,v,c]$. $N$ is the arithmetic conductor of the curve. $v$ gives the
 coordinate change for $E$ over $\Q$ to the minimal integral model (see
 \tet{ellminimalmodel}). Finally $c$ is the product of the local Tamagawa
 numbers $c_p$, a quantity which enters in the \idx{Birch and Swinnerton-Dyer
 conjecture}.\sidx{minimal model}
