=====Commutative regular rings===== Abbreviation: **CRRng** ====Definition==== A \emph{commutative regular ring} is a [[regular rings]] $\mathbf{R}=\langle R,+,-,0,\cdot,1 \rangle$ such that $\cdot$ is commutative: $x\cdot y=y\cdot x$ ==Morphisms== Let $\mathbf{R}$ and $\mathbf{S}$ be commutative regular rings. A morphism from $\mathbf{R}$ to $\mathbf{S}$ is a function $h:R\rightarrow S$ that is a homomorphism: $h(x+y)=h(x)+h(y)$, $h(x\cdot y)=h(x)\cdot h(y)$, $h(1)=1$ ====Examples==== Example 1: ====Basic results==== ====Properties==== ^[[Classtype]] |first-order | ^[[Equational theory]] | | ^[[Quasiequational theory]] | | ^[[First-order theory]] | | ^[[Locally finite]] |no | ^[[Residual size]] |unbounded | ^[[Congruence distributive]] | | ^[[Congruence modular]] |yes | ^[[Congruence n-permutable]] |yes, $n=2$ | ^[[Congruence regular]] |yes | ^[[Congruence uniform]] |yes | ^[[Congruence extension property]] | | ^[[Definable principal congruences]] | | ^[[Equationally def. pr. cong.]] | | ^[[Amalgamation property]] | | ^[[Strong amalgamation property]] | | ^[[Epimorphisms are surjective]] | | ====Finite members==== $\begin{array}{lr} f(1)= &1\\ f(2)= &\\ f(3)= &\\ f(4)= &\\ f(5)= &\\ f(6)= &\\ \end{array}$ ====Subclasses==== [[Fields]] ====Superclasses==== [[Commutative rings with identity]] ====References==== [(Ln19xx> )]