=====Gödel algebras===== Abbreviation: **GödA** ====Definition==== A \emph{Gödel algebra} is a [[Heyting algebras]] $\mathbf{A}=\langle A,\vee,0,\wedge,1,\rightarrow\rangle$ such that $(x\to y)\vee(y\to x)=1$ Remark: Gödel algebras are also called \emph{linear Heyting algebras} since subdirectly irreducible Gödel algebras are linearly ordered Heyting algebras. ====Definition==== A \emph{Gödel algebra} is a [[representable FLew-algebra]] $\mathbf{A}=\langle A, \vee, 0, \wedge, 1, \cdot, \rightarrow\rangle$ such that $x\wedge y=x\cdot y$ ==Morphisms== Let $\mathbf{A}$ and $\mathbf{B}$ be Gödel algebras. A morphism from $\mathbf{A}$ to $\mathbf{B}$ is a function $h:A\rightarrow B$ that is a homomorphism: $h(x\vee y)=h(x)\vee h(y)$, $h(0)=0$, $h(x\wedge y)=h(x)\wedge h(y)$, $h(1)=1$, $h(x\rightarrow y)=h(x)\rightarrow h(y)$ ====Examples==== Example 1: ====Basic results==== ====Properties==== ^[[Classtype]] |variety | ^[[Equational theory]] |decidable | ^[[Quasiequational theory]] |decidable | ^[[First-order theory]] | | ^[[Locally finite]] | | ^[[Residual size]] |countable | ^[[Congruence distributive]] |yes | ^[[Congruence modular]] |yes | ^[[Congruence n-permutable]] |yes, $n=2$ | ^[[Congruence e-regular]] |yes, $e=1$ | ^[[Congruence uniform]] | | ^[[Congruence extension property]] |yes | ^[[Definable principal congruences]] |yes | ^[[Equationally def. pr. cong.]] |yes | ^[[Amalgamation property]] | | ^[[Strong amalgamation property]] | | ^[[Epimorphisms are surjective]] | | ====Finite members==== $\begin{array}{lr} f(1)= &1\\ f(2)= &1\\ f(3)= &1\\ f(4)= &2\\ f(5)= &1\\ f(6)= &2\\ f(7)= &1\\ f(8)= &3\\ f(9)= &1\\ f(10)= &2\\ \end{array}$ ====Subclasses==== [[Boolean algebras]] ====Superclasses==== [[Heyting algebras]] ====References==== [(Ln19xx> )]