Freese and J6nsson [8] showed that the congruence lattice of a (universal) algebra in a congruence modular variety is always arguesian. On the other hand J6nsson [16] constructed arguesian lattices which cannot be embedded into the normal subgroup lattice of a group. These lattices consist of two arguesian planes of different prime order glued together over a two element sublattice (cf. Dilwort...

this paper is a chronological survey, with no proofs, of a direction in categorical algebra, which is based on categorical galois theory and involves generalized central extensions, commutators, and internal groupoids in barr exact mal’tsev and more general categories. galois theory proposes a notion of central extension, and motivates the study of internal groupoids, which is then used as an a...

This paper attempts to generalize universal algebras on classical sets to $L$-sets when $L$ is a GL-quantale. Some basic notions of fuzzy universal algebra on an $L$-set are introduced, such as subalgebra, quotient algebra, homomorphism, congruence, and direct product etc. The properties of them are studied. $L$-valued power algebra is also introduced and it is shown there is an onto homomorphi...

Many decisions in private and public organizations are made by groups. The paper explores strategies that the sponsor of a proposal may employ to convince a qualified majority of group members to approve the proposal. Adopting a mechanism design approach to communication, it emphasizes the need to distill information selectively to key members of the group and to engineer persuasion cascades in...

Abstract We consider a generalisation of the Basilica group to all odd primes: p -Basilica groups acting on -adic tree. show that have -congruence subgroup property but not congruence nor weak property. This provides first examples weakly branch with such properties. In addition, give branch, which are super strongly fractal. compute orders quotients these groups, enable us determine Hausdorff ...

We study the group of automorphisms of Shimura curves X0(D,N) attached to an Eichler order of square-free level N in an indefinite rational quaternion algebra of discriminant D > 1. We prove that, when the genus g of the curve is greater than or equal to 2, Aut(X0(D,N)) is a 2-elementary abelian group which contains the group of Atkin-Lehner involutions W0(D,N) as a subgroup of index 1 or 2. It...

Let G be a rank 2 complete affine or hyperbolic Kac–Moody group over a finite field k. Then G is locally compact and totally disconnected. Let B− = HU− be the negative minimal parabolic subgroup of G, where H is the analog of a diagonal subgroup and U− is generated by all negative real root groups. Let w1 and w2 be the generators of the Weyl group. Let P − 1 = B − t Bw1B be the negative standar...

(E;L) denotes an aÆne plane, (E;L; ) an ordered plane, and denotes the congruence relation on E E. If we assume (E;L; ) as an hyperbolic plane, there exists the corresponding theorem for hyperbolic planes (cf. [3]). For both proofs we consider rst the group of motions, in particular the line re ections. For the de nition of a motion and a line re ection we need only a congruence relation (cf. [...