=====Wajsberg hoops===== ====Definition==== A \emph{Wajsberg hoop} is a [[hoop]] $\mathbf{A}=\langle A, \cdot, \rightarrow, 1\rangle$ such that $(x\rightarrow y)\rightarrow y = (y\rightarrow x)\rightarrow x$ Remark: Lattice operations are term-definable by $x\wedge y=x\cdot(x\rightarrow y)$ and $x\vee y=(x\rightarrow y)\rightarrow y$. ==Morphisms== Let $\mathbf{A}$ and $\mathbf{B}$ be Wajsberg hoops. A morphism from $\mathbf{A}$ to $\mathbf{B}$ is a function $h:A\rightarrow B$ that is a homomorphism: $h(x\cdot y)=h(x)\cdot h(y)$, $h(x\rightarrow y)=h(x)\rightarrow h(y) $, $h(1)=1$ ====Examples==== Example 1: ====Basic results==== ====Properties==== ^[[Classtype]] |variety | ^[[Equational theory]] |decidable | ^[[Quasiequational theory]] | | ^[[First-order theory]] | | ^[[Locally finite]] |no | ^[[Residual size]] | | ^[[Congruence distributive]] |yes | ^[[Congruence modular]] |yes | ^[[Congruence n-permutable]] | | Congruence regular & yes Radim Belohlovek, \emph{On the regularity of MV-algebras and Wajsberg hoops}, Algebra Universalis, \textbf{44}, 2000, 375--377[[MRreview]]\\\hline ^[[Congruence uniform]] | | ^[[Congruence extension property]] | | ^[[Definable principal congruences]] | | ^[[Equationally def. pr. cong.]] | | ^[[Amalgamation property]] | | ^[[Strong amalgamation property]] | | ^[[Epimorphisms are surjective]] | | ====Finite members==== $\begin{array}{lr} f(1)= &1\\ f(2)= &1\\ f(3)= &\\ f(4)= &\\ f(5)= &\\ f(6)= &\\ f(7)= &\\ \end{array}$ ====Subclasses==== [[Generalized Boolean algebras]] [[MV-algebras]] ====Superclasses==== [[Hoops]] ====References==== [(Ln19xx> )]