The Modular Degree , Congruence Primes
نویسندگان
چکیده
The modular degree and congruence number are two fundamental invariants of an elliptic curve over the rational field. Frey and Müller have asked whether these invariants coincide. We find that the question has a negative answer, and show that in the counterexamples, multiplicity one (defined below) does not hold. At the same time, we prove a theorem about the relation between the two invariants: the modular degree divides the congruence number, and the ratio is divisible only by primes whose squares divide the conductor of the elliptic curve. We discuss the ratio even in the case where the square of a prime does divide the conductor, and we study analogues of the two invariants for modular abelian varieties of arbitrary dimension.
منابع مشابه
The Modular Degree, Congruence Primes and Multiplicity One
We answer a question of Frey and Müller about whether or not the modular degree and congruence number of elliptic curves are equal. We give examples in which they are not, prove a theorem relating them, and make a conjecture about the extent to which they differ. We also obtain relations between analogues of the modular degree and congruence number for modular abelian varieties, and give new ex...
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