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Theorem

Class Number Formula

Number Theory

The Class Number Formula relates several fundamental invariants of an algebraic number field, including its class number, regulator, and number of roots of unity, to a specific value of the field's own Dedekind zeta function. It is one of the central bridges between the arithmetic of a number field and the analytic behavior of its zeta function, generalizing simpler formulas already known for the field of rational numbers.

Facts
Partially Attested
Proof Year
1839 1
1839 is Dirichlet's proof for quadratic fields only, stated in the language of quadratic forms; the source gives no year for the general formula.
Statement
Relates many important invariants of an algebraic number field, including its class number, regulator, number of roots of unity and discriminant, to a special value of its Dedekind zeta function. 1
Classification
Statement Form
Identity or Equation 1
Connections

Has Statement Form

Equation, Concepts

Entity-backed identity for the statement-form enum value this theorem already carries, resolved to a mathematics concept by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The statement-form fact itself stays on the theorem unchanged.

Identity, Concepts

Entity-backed identity for the statement-form enum value this theorem already carries, resolved to a mathematics concept by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The statement-form fact itself stays on the theorem unchanged.

In Branch

Sources
1. Class number formula (Wikipedia)
  • Introduction
    the class number formula relates many important invariants of an algebraic number field to a special value of its Dedekind zeta function
  • Dirichlet class number formula
    published a proof of the class number formula for quadratic fields in 1839
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