# Birch and Swinnerton-Dyer conjecture

Let $E$ be an elliptic curve over $\mathbb{Q}$, and let $L(E,s)$ be the L-series attached to $E$.

###### Conjecture 1 (Birch and Swinnerton-Dyer).
1. 1.

$L(E,s)$ has a zero at $s=1$ of order equal to the rank of $E(\mathbb{Q})$.

2. 2.

Let $R=\operatorname{rank}(E(\mathbb{Q}))$. Then the residue of $L(E,s)$ at $s=1$, i.e. $\lim_{s\to 1}(s-1)^{-R}L(E,s)$ has a concrete expression involving the following invariants of $E$: the real period, the Tate-Shafarevich group, the elliptic regulator and the Neron model of $E$.

J. Tate said about this conjecture: “This remarkable conjecture relates the behavior of a function $L$ at a point where it is not at present known to be defined to the order of a group (Sha) which is not known to be finite!” The precise statement of the conjecture asserts that:

 $\lim_{s\to 1}\frac{L(E,s)}{(s-1)^{R}}=\frac{|\operatorname{Sha}|\cdot\Omega% \cdot\operatorname{Reg}(E/\mathbb{Q})\cdot\prod_{p}c_{p}}{|E_{\operatorname{% tors}}(\mathbb{Q})|^{2}}$

where

• $R$ is the rank of $E/\mathbb{Q}$.

• $\Omega$ is either the real period or twice the real period of a minimal model for $E$, depending on whether $E(\mathbb{R})$ is connected or not.

• $|\operatorname{Sha}|$ is the order of the Tate-Shafarevich group of $E/\mathbb{Q}$.

• $\operatorname{Reg}(E/\mathbb{Q})$ is the http://planetmath.org/node/RegulatorOfAnEllipticCurveelliptic regulator of $E(\mathbb{Q})$.

• $|E_{\operatorname{tors}}(\mathbb{Q})|$ is the number of torsion points on $E/\mathbb{Q}$ (including the point at infinity $O$).

• $c_{p}$ is an elementary local factor, equal to the cardinality of $E(\mathbb{Q}_{p})/E_{0}(\mathbb{Q}_{p})$, where $E_{0}(\mathbb{Q}_{p})$ is the set of points in $E(\mathbb{Q}_{p})$ whose reduction modulo $p$ is non-singular in $E(\mathbb{F}_{p})$. Notice that if $p$ is a prime of good reduction for $E/\mathbb{Q}$ then $c_{p}=1$, so only $c_{p}\neq 1$ only for finitely many primes $p$. The number $c_{p}$ is usually called the Tamagawa number of $E$ at $p$.

The following is an easy consequence of the B-SD conjecture:

###### Conjecture 2 (Parity Conjecture).

The root number of $E$, denoted by $w$, indicates the parity of the rank of the elliptic curve, this is, $w=1$ if and only if the rank is even.

There has been a great amount of research towards the B-SD conjecture. For example, there are some particular cases which are already known:

###### Theorem 1 (Coates, Wiles).

Suppose $E$ is an elliptic curve defined over an imaginary quadratic field $K$, with complex multiplication by $K$, and $L(E,s)$ is the L-series of $E$. If $L(E,1)\neq 0$ then $E(K)$ is finite.

## References

• 1 Claymath Institute, Description, http://www.claymath.org/millennium/Birch_and_Swinnerton-Dyer_Conjecture/online.
• 2 J. Coates, A. Wiles, On the Conjecture of Birch and Swinnerton-Dyer, Inv. Math. 39, 223-251 (1977).
• 3 Keith Devlin, The Millennium Problems: The Seven Greatest Unsolved Mathematical Puzzles of Our Time, 189 - 212, Perseus Books Group, New York (2002).
• 4 James Milne, Elliptic Curves, http://www.jmilne.org/math/CourseNotes/math679.htmlonline course notes.
• 5 Joseph H. Silverman, . Springer-Verlag, New York, 1986.
• 6 Joseph H. Silverman, Advanced Topics in the Arithmetic of Elliptic Curves. Springer-Verlag, New York, 1994.
 Title Birch and Swinnerton-Dyer conjecture Canonical name BirchAndSwinnertonDyerConjecture Date of creation 2013-03-22 13:49:46 Last modified on 2013-03-22 13:49:46 Owner alozano (2414) Last modified by alozano (2414) Numerical id 16 Author alozano (2414) Entry type Conjecture Classification msc 14H52 Synonym BS-D conjecture Related topic EllipticCurve Related topic RegulatorOfAnEllipticCurve Related topic MordellCurve Related topic ArithmeticOfEllipticCurves Defines Birch and Swinnerton-Dyer conjecture Defines parity conjecture