In this note we characterize all subalgebras and homomorphic images of the free cyclic Heyting algebra, also known as the RiegerNishimura lattice N . Consequently, we prove that every subalgebra of N is projective, that a finite Heyting algebra is a subalgebra of N iff it is projective, and characterize projective homomorphic images of N . The atoms and co-atoms of the lattice of all subalgebra...

In this paper, we review the behaviour of the Frattini subgroup Φ(G) and the Frattini factor group G/Φ(G) of an infinite group G having in mind the most standard results of the finite case. Este art́ıculo está dedicado con todo cariño a la memoria de Chicho. Al no formar parte de tu grupo de investigación, no tuve la fortuna de relacionarme contigo por este motivo, pero śı que tuve la oportunida...

Let G be a finite group of even order v. Does there exist a 1−factorization of Kv admitting G as an automorphism group acting sharply transitively on vertices? If G is cyclic and v = 2, for t ≥ 3, then the answer to the previous question is known to be negative by a result of A.Hartman and A.Rosa (1985). For several large families of groups of even order constructions have always been found thu...

Let G = A ∗H B be the generalized free product of the groups A and B with the amalgamated subgroup H. Also, let λ(G) and ψ(G) represent the lower near Frattini subgroup of G and the near Frattini subgroup of G respectively. We show that G is ψ−free provided: (i) G is any ordinary free product of groups; (ii) G = A ∗H B and there exists an element c in G\H such thatH ∩H = 1; (iii) G = A ∗H B and...

All groups considered are finite. Given a group G, the Frattini subgroup of G, Q(G) is defined to be the intersection of all maximal subgroups of G. There has been much interest in generalizing the Frattini subgroup in various ways, and in investigating their influence on the structure of the group (see [3,.5,8,12,13]). These generalizations were done taking into account the following question:...

Let G = A HB be the generalized free product of the groups A and B with the amalgamated subgroup H. Also, let λ(G) and ψ(G) represent the lower near Frattini subgroup and the near Frattini subgroup of G, respectively. If G is finitely generated and residually finite, then we show that ψ(G) ≤ H, provided H satisfies a nontrivial identical relation. Also, we prove that if G is residually finite, ...

Given a finite group G, let PG(s) be the probability that s randomly chosen elements generate G, and let H be a finite group with PG(s) = PH(s). We show that if the nonabelian composition factors of G and H are PSL(2, p) for some non-Mersenne prime p ≥ 5, then G and H have the same non-Frattini chief factors. Mathematics Subject Classification (2010). 20D06.