Non-isomorphic semigroups with isomorphic semigroups of subsets.
Non-looping string rewriting
Non-Looping String Rewriting
String rewriting reductions of the form , called loops, are the most frequent cause of infinite reductions (non- termination). Regarded as a model of computation, infinite reductions are unwanted whence their static detection is important. There are string rewriting systems which admit infinite reductions although they admit no loops. Their non-termination is particularly difficult to uncover. We present a few necessary conditions for the existence of loops, and thus establish a means...
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-minimal modular symbols for GL(n).
Non-modular congruence lattices of Rees matrix semigroups
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.
Nonsingular semilattices and semigroups
Nonsplitting F-quasigroups
T. Kepka, M.K. Kinyon and J.D. Phillips: The structure of F-quasigroups, J. Algebra 317 (2007), no. 2, 435–461 developed a connection between F-quasigroups and NK-loops. Since NK-loops are contained in the variety generated by groups and commutative Moufang loops, a question that arises is whether or not there exists a nonsplit NK-loop and likewise a nonsplit F-quasigroup. Here we prove that there do indeed exist nonsplit F-quasigroups and show that there are exactly four corresponding nonsplit...
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...
Nonsymmetric group algebras
Non-symmetric Hall-Littlewood polynomials.
Non-unique factorizations in block semigroups and arithmetical applications
Non-unique factorizations in orders of global fields.
Non-uniqueness of homotopy factorizations into irreducible polyhedra
Normal all pseudo-Anosov subgroups of mapping class groups.
Normal and Power Endomorphisms of a Group.