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Abelian lattice-ordered groups
Abbreviation: AbLGrp
Definition
An \emph{abelian lattice-ordered group} (or abelian ℓ\emph{-group}) is a lattice-ordered group L=⟨L,∨,∧,⋅,−1,e⟩ such that
⋅ is commutative: x⋅y=y⋅x
Morphisms
Let L and M be ℓ-groups. A morphism from L to M is a function f:L→M that is a homomorphism: f(x∨y)=f(x)∨f(y) and f(x⋅y)=f(x)⋅f(y).
Remark: It follows that f(x∧y)=f(x)∧f(y), f(x−1)=f(x)−1, and f(e)=e
Definition
An \emph{abelian lattice-ordered group} (or \emph{abelian ℓ-group}) is a commutative residuated lattice L=⟨L,∨,∧,⋅,→,e⟩ that satisfies the identity x⋅(x→e)=e.
Remark: x−1=x→e and x→y=x−1y
Examples
⟨Z,max,min,+,−,0⟩, the integers with maximum, minimum, addition, unary subtraction and zero. The variety of abelian ℓ-groups is generated by this algebra.
Basic results
The lattice reducts of (abelian) ℓ-groups are distributive lattices.
Properties
| Classtype | variety |
|---|---|
| Equational theory | decidable |
| Quasiequational theory | decidable |
| First-order theory | hereditarily undecidable 1) 2) |
| Locally finite | no |
| Residual size | |
| Congruence distributive | yes (see lattices) |
| Congruence modular | yes |
| Congruence n-permutable | yes, n=2 (see groups) |
| Congruence regular | yes, (see groups) |
| Congruence uniform | yes, (see groups) |
| Congruence extension property | |
| Definable principal congruences | |
| Equationally def. pr. cong. | |
| Amalgamation property | yes |
| Strong amalgamation property | no 3) |
| Epimorphisms are surjective |
Finite members
None