# Kernel congruence

From Encyclopedia of Mathematics

*of a homomorphism $\phi : A \rightarrow A'$ of algebraic systems*

The congruence (cf. Congruence (in algebra)) $\theta$ on $A$ consisting of all pairs $(a,b) \in A \times A$ for which $\phi(a) = \phi(b)$. For any congruence $\theta$ on an algebraic system there is a homomorphism $\phi$ of this system for which $\theta$ is the kernel congruence. If $\theta$ is the kernel congruence of a strong homomorphism $\phi$ of an algebraic system $A$ onto a system $A'$, then the canonical mapping $a/\theta \mapsto \phi(a)$, where $a/\theta = \{ b \in A : (b,a) \in \theta \}$, is an isomorphism of the quotient system $A/\theta$ onto $A'$.

For references see Homomorphism.

**How to Cite This Entry:**

Kernel congruence.

*Encyclopedia of Mathematics.*URL: http://encyclopediaofmath.org/index.php?title=Kernel_congruence&oldid=11822

This article was adapted from an original article by D.M. Smirnov (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article