mathlib documentation


Dedekind domains #

This file defines the notion of a Dedekind domain (or Dedekind ring), as a Noetherian integrally closed commutative ring of Krull dimension at most one.

Main definitions #

Implementation notes #

The definitions that involve a field of fractions choose a canonical field of fractions, but are independent of that choice. The ..._iff lemmas express this independence.

Often, definitions assume that Dedekind domains are not fields. We found it more practical to add a (h : ¬ is_field A) assumption whenever this is explicitly needed.

References #

Tags #

dedekind domain, dedekind ring

def ring.dimension_le_one (R : Type u_1) [comm_ring R] :

A ring R has Krull dimension at most one if all nonzero prime ideals are maximal.

theorem ring.dimension_le_one.is_integral_closure (R : Type u_1) (A : Type u_2) [comm_ring R] [comm_ring A] (B : Type u_3) [comm_ring B] [is_domain B] [nontrivial R] [algebra R A] [algebra R B] [algebra B A] [is_scalar_tower R B A] [is_integral_closure B R A] (h : ring.dimension_le_one R) :
structure is_dedekind_domain (A : Type u_2) [comm_ring A] [is_domain A] :

A Dedekind domain is an integral domain that is Noetherian, integrally closed, and has Krull dimension at most one.

This is definition 3.2 of [Neu99].

The integral closure condition is independent of the choice of field of fractions: use is_dedekind_domain_iff to prove is_dedekind_domain for a given fraction_map.

This is the default implementation, but there are equivalent definitions, is_dedekind_domain_dvr and is_dedekind_domain_inv. TODO: Prove that these are actually equivalent definitions.

Instances of this typeclass
theorem is_dedekind_domain_iff (A : Type u_2) [comm_ring A] [is_domain A] (K : Type u_1) [field K] [algebra A K] [is_fraction_ring A K] :

An integral domain is a Dedekind domain iff and only if it is Noetherian, has dimension ≤ 1, and is integrally closed in a given fraction field. In particular, this definition does not depend on the choice of this fraction field.