A note on lattice congruence regularization

2001 ◽  
Vol 46 (1) ◽  
pp. 187-191
Author(s):  
Harry Lakser
Keyword(s):  
Lattice Congruence

scholarly journals The facial weak order in finite Coxeter groups

2020 ◽  
Vol DMTCS Proceedings, 28th... ◽  
Author(s):  
Aram Dermenjian ◽  
Christophe Hohlweg ◽  
Vincent Pilaud
Keyword(s):  
Coxeter Group ◽  
Coxeter Groups ◽  
Geometric Interpretation ◽  
Weak Order ◽  
Maximal Length ◽  
Lattice Congruence ◽  
Finite Coxeter Group ◽  
International Audience

International audience We investigate a poset structure that extends the weak order on a finite Coxeter group W to the set of all faces of the permutahedron of W. We call this order the facial weak order. We first provide two alternative characterizations of this poset: a first one, geometric, that generalizes the notion of inversion sets of roots, and a second one, combinatorial, that uses comparisons of the minimal and maximal length representatives of the cosets. These characterizations are then used to show that the facial weak order is in fact a lattice, generalizing a well-known result of A. Bjo ̈rner for the classical weak order. Finally, we show that any lattice congruence of the classical weak order induces a lattice congruence of the facial weak order, and we give a geometric interpretation of its classes.

S-Lattice Congruences of S-Lattices

2012 ◽  
Vol 19 (03) ◽  
pp. 465-472
Author(s):  
Congwen Luo
Keyword(s):  
Distributive Lattice ◽  
Lattice Congruence ◽  
Ordered Semigroups

In this paper, the S-lattices are introduced as a representation of lattice-ordered monoids. The smallest S-lattice congruence induced by a relation on an S-lattice is characterized and the correspondence between the S-lattice congruences and S-ideals in an S-distributive lattice is discussed. These generalize some recent results of lattices and lattice-ordered semigroups.

scholarly journals Lattice subgroups of free congruence groups

1969 ◽  
Vol 10 (2) ◽  
pp. 106-115 ◽  
Author(s):  
A. W. Mason
Keyword(s):  
Upper Bound ◽  
Modular Group ◽  
Congruence Subgroup ◽  
Principal Congruence ◽  
Lattice Congruence ◽  
Congruence Group ◽  
Integral Matrices ◽  
Principal Congruence Subgroup ◽  
Lattice Subgroup ◽  
Lattice Subgroups

Let Г(1) denote the homogeneous modular group of 2 × 2 matrices with integral entries and determinant 1. Let (1) be the inhomogeneous modular group of 2 × 2 integral matrices of determinant 1 in which a matrix is identified with its negative. (N), the principal congruence subgroup of level N, is the subgroup of (1) consisting of all T ∈ (1) for which T ≡ ± I (mod N), where N is a positive integer and I is the identity matrix. A subgroup of (1) is said to be a congruence group of level N if contains (N) and N is the least such integer. Similarly, we denote by Г(N) the principal congruence subgroup of level N of Г(1), consisting of those T∈(1) for which T ≡ I (mod N), and we say that a sub group of Г(1) is a congruence group of level N if contains Г (N) and N is minimal with respect to this property. In a recent paper [9] Rankin considered lattice subgroups of a free congruence subgroup of rank n of (1). By a lattice subgroup of we mean a subgroup of which contains the commutator group . In particular, he showed that, if is a congruence group of level N and if is a lattice congruence subgroup of of level qr, where r is the largest divisor of qr prime to N, then N divides q and r divides 12. He then posed the problem of finding an upper bound for the factor q. It is the purpose of this paper to find such an upper bound for q. We also consider bounds for the factor r.

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