=====Rectangular bands===== Abbreviation: **RBand** ====Definition==== A \emph{rectangular band} is a [[bands]] $\mathbf{B}=\langle B,\cdot \rangle $ such that $\cdot $ is rectangular: $x\cdot y\cdot x=x$. ====Definition==== A \emph{rectangular band} is a [[bands]] $\mathbf{B}=\langle B,\cdot \rangle $ such that $x\cdot y\cdot z=x\cdot z$. ==Morphisms== Let $\mathbf{B}$ and $\mathbf{C}$ be rectangular bands. A morphism from $\mathbf{B}$ to $\mathbf{C}$ is a function $h:B\rightarrow C$ that is a homomorphism: $h(xy)=h(x)h(y)$ ====Examples==== ====Basic results==== ====Properties==== ^[[Classtype]] |variety | ^[[Equational theory]] |decidable in polynomial time | ^[[Quasiequational theory]] | | ^[[First-order theory]] | | ^[[Locally finite]] |yes | ^[[Residual size]] | | ^[[Congruence distributive]] | | ^[[Congruence modular]] | | ^[[Congruence n-permutable]] | | ^[[Congruence regular]] | | ^[[Congruence uniform]] | | ^[[Congruence extension property]] | | ^[[Definable principal congruences]] | | ^[[Equationally def. pr. cong.]] | | ^[[Amalgamation property]] | | ^[[Strong amalgamation property]] | | ^[[Epimorphisms are surjective]] | | ====Finite members==== $\begin{array}{lr} f(1)= &1\\ f(2)= &\\ f(3)= &\\ f(4)= &\\ f(5)= &\\ f(6)= &\\ f(7)= &\\ \end{array}$ ====Subclasses==== [[Left-zero semigroups]] [[Right-zero semigroups]] ====Superclasses==== [[Normal bands]] ====References==== [(Ln19xx> )]