Noncrossing partitions, clusters and the Coxeter plane.
Non-free two-generator subgroups of SL2(Q).
The question of whether two parabolic elements A, B of SL2(C) are a free basis for the group they generate is considered. Some known results are generalized, using the parameter τ = tr(AB) - 2. If τ = a/b ∈ Q, |τ| < 4, and |a| ≤ 16, then the group is not free. If the subgroup generated by b in Z / aZ has a set of representatives, each of which divides one of b ± 1, then the subgroup of SL2(C) will not be free.
Non-gatherable triples for non-affine root systems.
Non-hyperbolicity in random regular graphs and their traffic characteristics
In this paper we prove that random d-regular graphs with d ≥ 3 have traffic congestion of the order O(n logd−13 n) where n is the number of nodes and geodesic routing is used. We also show that these graphs are not asymptotically δ-hyperbolic for any non-negative δ almost surely as n → ∞.
Non-maximal cyclic group actions on compact Riemann surfaces.
We say that a finite group G of automorphisms of a Riemann surface X is non-maximal in genus g if (i) G acts as a group of automorphisms of some compact Riemann surface Xg of genus g and (ii), for all such surfaces Xg , |Aut Xg| > |G|. In this paper we investigate the case where G is a cyclic group Cn of order n. If Cn acts on only finitely many surfaces of genus g, then we completely solve the problem of finding all such pairs (n,g).
Non-nilpotent subgroups of locally graded groups
We show that a locally graded group with a finite number m of non-(nilpotent of class at most n) subgroups is (soluble of class at most [log₂n] + m + 3)-by-(finite of order ≤ m!). We also show that the derived length of a soluble group with a finite number m of non-(nilpotent of class at most n) subgroups is at most [log₂ n] + m + 1.
Nonpositive immersions, sectional curvature, and subgroup properties.
Nonpositively curved 2-complexes with isolated flats.
Non-positively curved aspects of Artin groups of finite type.
Non-standard automorphisms of branched coverings of a disk and a sphere
Let Y be a closed 2-dimensional disk or a 2-sphere. We consider a simple, d-sheeted branched covering π: X → Y. We fix a base point A₀ in Y (A₀ ∈ ∂Y if Y is a disk). We consider the homeomorphisms h of Y which fix ∂Y pointwise and lift to homeomorphisms ϕ of X-the automorphisms of π. We prove that if Y is a sphere then every such ϕ is isotopic by a fiber-preserving isotopy to an automorphism which fixes the fiber pointwise. If Y is a disk, we describe explicitly a small set of automorphisms of...
Normal all pseudo-Anosov subgroups of mapping class groups.
Normal subgroups as ideals
Normal-convexity and equations over groups.
Normally constrained -groups
In questo lavoro si studiano i gruppi finiti di ordine una potenza di un numero primo in cui i sottogruppi normali sono compresi tra due termini successivi della serie centrale discendente. Si ottengono numerose proprietà generali di questi gruppi, e una loro dettagliata descrizione in classe di nilpotenza 2.
Normalteiler ganzzahliger Spingruppen.
Note on generalizing pregroups.
Note on the simple group of order 504
Numerical invariants of exponential groups and locally free approximation of the braid group.
On a class of groups with strongly embedded subgroup.
On a class of residually finite groups.