Abelian variety

Definition

An abelian variety is a complete algebraic variety that has a group structure, meaning it allows for the addition of its points, and is defined over an algebraically closed field. This concept plays a crucial role in understanding the properties of elliptic curves, isogenies, and more complex structures like Jacobian varieties, connecting various areas of arithmetic geometry.

5 Must Know Facts For Your Next Test

1. Abelian varieties generalize elliptic curves to higher dimensions, allowing for the study of more complex algebraic structures.
2. They can be defined over any field, but most importantly, they retain properties when base changed to algebraically closed fields.
3. The group structure on an abelian variety can be analyzed through its endomorphisms, which are important for understanding its arithmetic properties.
4. Every abelian variety can be expressed as a product of simple abelian varieties, providing a way to classify them according to their structure.
5. Abelian varieties play a significant role in the context of l-adic representations and Néron models, linking geometry with number theory.

Review Questions

• How does the concept of an abelian variety enhance the understanding of elliptic curves and their isogenies?
  • Abelian varieties encompass elliptic curves as special cases, allowing for a broader framework in which to study their properties. The group structure of abelian varieties facilitates the definition and analysis of isogenies, which are morphisms that preserve this structure. By understanding isogenies in the context of abelian varieties, one can explore deeper connections between different elliptic curves and their geometric properties.
• Discuss the significance of endomorphism algebras in relation to abelian varieties.
  • Endomorphism algebras consist of all morphisms from an abelian variety to itself that preserve its group structure. These algebras provide crucial insights into the arithmetic and geometric properties of the abelian variety. The structure of these endomorphism algebras can reveal information about how the variety behaves under certain operations, making them essential for understanding its classification and applications in number theory.
• Evaluate how abelian varieties relate to Néron models and their importance in arithmetic geometry.
  • Abelian varieties are intimately connected to Néron models, which provide a way to study these varieties over local and global fields. The construction of Néron models allows mathematicians to analyze how abelian varieties behave in families and helps extend results from characteristic zero settings to those in positive characteristic. This relationship highlights the interplay between geometry and number theory, enriching our understanding of both fields and facilitating advancements in topics like reduction theory and moduli spaces.

Related terms

Elliptic Curve: An elliptic curve is a smooth, projective algebraic curve of genus one with a specified point, serving as a fundamental example of an abelian variety.

Isogeny: An isogeny is a morphism between abelian varieties that preserves the group structure, allowing one to relate different abelian varieties through their properties.

Jacobian Variety: A Jacobian variety is a specific type of abelian variety that arises from algebraic curves and encodes information about the curve's divisors and linear equivalence classes.