Conductor of an abelian variety (reviewed)

The conductor of an abelian variety $A$ over $\Q$ is a positive integer $N$ whose prime factors are the primes $p$ where $A$ has bad reduction. The power to which $p$ divides $N$ depends on the type of bad reduction, and is related to the ramification in the $p$-torsion field of the abelian variety.

The conductor of an abelian variety over a number field is defined similarly; it is an ideal that is a product of non-trivial powers of the prime ideals where $A$ has bad reduction. The conductor of a curve $C$ over a number field is defined to be the conductor of the Jacobian of $C$.

The conductor is an invariant of the isogeny class of an abelian variety.