nLab algebraic number theory







Algebraic number theory studies algebraic numbers, number fields and related algebraic structures.

An algebraic number is a root of a polynomial equation with integer coefficients (or, equivalently with rational coeffients). An algebraic integer is a root of a monic polynomial with integer coefficients. Given a field kk a (algebraic) number field K=k[P]K = k[P] over kk is the minimal field containing all the roots of a given polynomial PP with coefficients in kk. Usually one considers algebraic number fields over rational numbers.

The main direction in algebraic number theory is the class field theory which roughly studies finite abelian extensions of number fields. The one dimensional class field theory stems from the ideas of Kronecker and Weber, and results of Hilbert soon after them. Main results of the theory belong to the first half of the 20th century (Hilbert, Artin, Tate, Hasse…) and are quite different for the local field from the global field case. Generalizations for higher dimensional fields came later under now active higher class field theory, which is usually formulated in terms of algebraic K-theory and is closely related to deep questions of algebraic geometry (Tate, Kato, Saito etc.).


The following survey of Connes-Marcolli work has an accessible quick introduction to algebraic number theory

  • P. Almeida, Noncommutative geometry and arithmetics, Russian Journal of Mathematical Physics 16, No. 3, 2009, pp. 350–362, doi, see also nLab:arithmetic and noncommutative geometry

See also

  • Alexander Schmidt, Higher dimensional class field theory from a topological point of view, page

Last revised on March 12, 2024 at 09:32:42. See the history of this page for a list of all contributions to it.