The variety bpO consists of those algebras （L; ∧,∨, f,＊ ） of type 〈2,2,1, 1,0,0〉 where （L; ∧,∨, f, 0, 1） is an Ockham algebra, （L; ∧,∨, ＊, 0, 1） is a p-algebra, and the operations x → f（x） and x →...The variety bpO consists of those algebras （L; ∧,∨, f,＊ ） of type 〈2,2,1, 1,0,0〉 where （L; ∧,∨, f, 0, 1） is an Ockham algebra, （L; ∧,∨, ＊, 0, 1） is a p-algebra, and the operations x → f（x） and x → x^＊ satisfy the identities f（x^＊） = x^＊＊ and [f（x）]^＊ = f^2（x）. In this note, we show that the compact congruences on a bpO-algebra form a dual Stone lattice. Using this, we characterize the algebras in which every principal congruence is complemented. We also give a description of congruence coherent bpO-algebras.展开更多
Here we introduce a subclass of the class of Ockham algebras （L; f） for which L satisfies the property that for every x ∈ L, there exists n 〉 0 such that fn（x） and f^n＋1（x） are complementary. We characterize ...Here we introduce a subclass of the class of Ockham algebras （L; f） for which L satisfies the property that for every x ∈ L, there exists n 〉 0 such that fn（x） and f^n＋1（x） are complementary. We characterize the structure of the lattice of congruences on such an algebra （L; f）. We show that the lattice of compact congruences on L is a dual Stone lattice, and in particular, that the lattice Con L of congruences on L is boolean if and only if L is finite boolean. We also show that L is congruence coherent if and only if it is boolean. Finally, we give a sufficient and necessary condition to have the subdirectly irreducible chains.展开更多
In this paper,we study a certain class of double Ockham algebras (L;∧,∨,f,k,0,1), namely the bounded distributive lattices (L;∧,∨,0,1) endowed with a commuting pair of unary op- erations f and k,both of which are ...In this paper,we study a certain class of double Ockham algebras (L;∧,∨,f,k,0,1), namely the bounded distributive lattices (L;∧,∨,0,1) endowed with a commuting pair of unary op- erations f and k,both of which are dual endomorphisms.We characterize the subdirectly irreducible members,and also consider the special case when both (L;f) and (L;k) are de Morgan algebras.We show via Priestley duality that there are precisely nine non-isomorphic subdirectly irreducible members, all of which are simple.展开更多
The variety ddpM of de Morgan algebras with double demi-pseudocomplementation consists of those algebras （L; ∧ , ∨ , , , ＋ , 0, 1） of type （2, 2, 1, 1, 1, 0, 0） where （L; ∧ , ∨ , , 0, 1） is a de Morgan alge...The variety ddpM of de Morgan algebras with double demi-pseudocomplementation consists of those algebras （L; ∧ , ∨ , , , ＋ , 0, 1） of type （2, 2, 1, 1, 1, 0, 0） where （L; ∧ , ∨ , , 0, 1） is a de Morgan algebra, （L; ∧ , ∨ , , ＋ , 0, 1） is a double demi-p-lattice and the operations x → x , x → x and x → x ＋ are linked by the identities x = x , x ＋ = x ＋ and x ＋ = x ＋ . In this paper, we characterize congruences on a ddpM-algebra, and give a description of the subdirectly irreducible algebras.展开更多
The variety eO of extended Ockham algebras consists of those algebras （L; ∧, ∨, f, k, 0, 1） such that （L; ∧, ∨, 0, 1） is a bounded distributive lattice together with a dual endomorphism f on L and an endomorp...The variety eO of extended Ockham algebras consists of those algebras （L; ∧, ∨, f, k, 0, 1） such that （L; ∧, ∨, 0, 1） is a bounded distributive lattice together with a dual endomorphism f on L and an endomorphism k on L such that fk = kf. In this paper we extend Urquhart＇s theorem to eO-algebras and we are in particular concerned with the subclass e2M of eO-algebras in which f^2 = id and k^2 = id. We show that there are 19 non-equivalent axioms in e2M and then order them by implication.展开更多
文摘The variety bpO consists of those algebras （L; ∧,∨, f,＊ ） of type 〈2,2,1, 1,0,0〉 where （L; ∧,∨, f, 0, 1） is an Ockham algebra, （L; ∧,∨, ＊, 0, 1） is a p-algebra, and the operations x → f（x） and x → x^＊ satisfy the identities f（x^＊） = x^＊＊ and [f（x）]^＊ = f^2（x）. In this note, we show that the compact congruences on a bpO-algebra form a dual Stone lattice. Using this, we characterize the algebras in which every principal congruence is complemented. We also give a description of congruence coherent bpO-algebras.
文摘Here we introduce a subclass of the class of Ockham algebras （L; f） for which L satisfies the property that for every x ∈ L, there exists n 〉 0 such that fn（x） and f^n＋1（x） are complementary. We characterize the structure of the lattice of congruences on such an algebra （L; f）. We show that the lattice of compact congruences on L is a dual Stone lattice, and in particular, that the lattice Con L of congruences on L is boolean if and only if L is finite boolean. We also show that L is congruence coherent if and only if it is boolean. Finally, we give a sufficient and necessary condition to have the subdirectly irreducible chains.
文摘In this paper,we study a certain class of double Ockham algebras (L;∧,∨,f,k,0,1), namely the bounded distributive lattices (L;∧,∨,0,1) endowed with a commuting pair of unary op- erations f and k,both of which are dual endomorphisms.We characterize the subdirectly irreducible members,and also consider the special case when both (L;f) and (L;k) are de Morgan algebras.We show via Priestley duality that there are precisely nine non-isomorphic subdirectly irreducible members, all of which are simple.
文摘The variety ddpM of de Morgan algebras with double demi-pseudocomplementation consists of those algebras （L; ∧ , ∨ , , , ＋ , 0, 1） of type （2, 2, 1, 1, 1, 0, 0） where （L; ∧ , ∨ , , 0, 1） is a de Morgan algebra, （L; ∧ , ∨ , , ＋ , 0, 1） is a double demi-p-lattice and the operations x → x , x → x and x → x ＋ are linked by the identities x = x , x ＋ = x ＋ and x ＋ = x ＋ . In this paper, we characterize congruences on a ddpM-algebra, and give a description of the subdirectly irreducible algebras.
文摘The variety eO of extended Ockham algebras consists of those algebras （L; ∧, ∨, f, k, 0, 1） such that （L; ∧, ∨, 0, 1） is a bounded distributive lattice together with a dual endomorphism f on L and an endomorphism k on L such that fk = kf. In this paper we extend Urquhart＇s theorem to eO-algebras and we are in particular concerned with the subclass e2M of eO-algebras in which f^2 = id and k^2 = id. We show that there are 19 non-equivalent axioms in e2M and then order them by implication.
