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Hasse's bound for elliptic curves over finite fields (Theorem)

Let $ E$ be an elliptic curve defined over a finite field $ \mathbb{F}_q$ with $ q=p^r$ elements ( $ p\in\mathbb{Z}$ is a prime). The following theorem gives a bound of the size of $ E(\mathbb{F}_q)$, $ N_q$, i.e. the number points of $ E$ defined over $ \mathbb{F}_q$. This was first conjectured by Emil Artin (in his thesis!) and proved by Helmut Hasse in the 1930's.

Theorem 1 (Hasse)  
$\displaystyle \mid N_q -q -1 \mid \leq 2\sqrt{q} $

Remark: Let $ a_p=p+1-N_p$ as in the definition of the L-series of an ellitpic curve. Then Hasse's bound reads:

$\displaystyle \mid a_p \mid \leq 2\sqrt{p}$

This fact is key for the convergence of the L-series of $ E$.



"Hasse's bound for elliptic curves over finite fields" is owned by alozano.
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See Also: L-series of an elliptic curve, elliptic curve, bad reduction, the arithmetic of elliptic curves

Other names:  Hasse's bound
Keywords:  number of points, finite field
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Cross-references: curve, points, size, bound, prime, finite field, elliptic curve
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This is version 2 of Hasse's bound for elliptic curves over finite fields, born on 2003-09-03, modified 2003-09-04.
Object id is 4686, canonical name is HassesBoundForEllipticCurvesOverFiniteFields.
Accessed 2981 times total.

Classification:
AMS MSC14H52 (Algebraic geometry :: Curves :: Elliptic curves)

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