## Abstract

A new class of partial order-types, class G+ bqo is defined and investigated here. A poset P is in the class G+_ iff the poset algebra F(P) is generated by a better quasi-order G that is included in L(P). The free Boolean algebra F(P) and its free distributive lattice L(P) have been defined in [ABKR]. The free Boolean algebra F(P) contains the partial order P and is generated by it: F(P) has the following universal property. If B is any Boolean algebra and f is any order-preserving map from P into a Boolean algebra B, then f can be extended to a homomorphism f of F(P) into B. We also define L(P) as the sublattice of F(P) generated by P. We prove that if P is any well quasi-ordering, then L(P) is well founded, and is a countable union of well quasi-orderings. We prove that the class G+_bqo is contained in the class of well quasi-ordered sets. We prove that G+_bqo is preserved under homomorphic image, finite products, and lexicographic sum over better quasi-ordered index sets. We prove also that every countable well quasi-ordered set is in G+bqo. We do not know, however if the class of well quasi-ordered sets is contained in G+_bqo . Additional results concern homomorphic images of posets algebras.

Original language | English |
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Pages (from-to) | 263-286 |

Number of pages | 24 |

Journal | Algebra Universalis |

Volume | 58 |

Issue number | 3 |

DOIs | |

State | Published - 1 Jun 2008 |

## Keywords

- Better quasi-orderings (bqo)
- Poset algebras
- Superatomic Boolean algebras
- Well quasi-orderings (wqo)

## ASJC Scopus subject areas

- Algebra and Number Theory
- Logic