(Cyclic) subgroup separability of HNN and split extensions

This work has been divided in two parts. In the first part we give a sufficient conditions on an HNN extension of a free group to be cyclic subgroup seperable. In the second part we define just subgroup separability on a split extension of special groups which is actually on holomorph.      

Residual finiteness, subgroup separability and conjugacy separability of certain HNN extensions

In this note we shall give characterisations for HNN extensions of non-cyclic polycyclic-by-finite groups with normal infinite cyclic associated subgroups to be residually finite, subgroup separable and conjugacy separable.     

Conjugacy Separability of Certain HNN Extensions of Conjugacy-Separable Groups

A group G is said to be conjugacy-separable if, for each pair of elements x, y G such that x and y are not conjugate in G, there exists a finite homomorphic image G¯ of G such that the images of x and y are not conjugate in G¯. In this paper, we show that certain HNN extensions of conjugacy-separable groups are conjugacy-separable. We then apply our results to HNN extensions of polycyclic-by-finite groups.2000 Mathematics Subject Classification: primary 20E26, 20E06; secondary 20F05     

A note on the conjugacy classes of non-cyclic subgroups

Let G be a finite group and δ(G) denote the number of conjugacy classes of all non-cyclic subgroups of G. The symbol π(G) denotes the set of the prime divisors of |G|. In [7 Meng, W., Li, S. R. (2014). Finite groups with few conjugacy classes of non-cyclic subgroups. Scientia Sin. Math. 44:939–944.[Crossref] , [Google Scholar]], Meng and Li showed the inequality δ(G)≥2^|π(G)|?2, where G is non-cyclic solvable group. In this paper, we describe the finite groups G such that δ(G) = 2^|π(G)|?2. Another aim of this paper would show δ(G)≥M(G)+2 for unsolvable groups G and the equality holds ?G?A₅ or SL(2,5), where M(G) denotes the number of conjugacy classes of all maximal subgroups of G.     

On the number of certain Galois extensions of local fields

In this paper, we will calculate the number of Galois extensions of local fields with Galois group or .

     

Fundamental Groups of Graphs of Cyclic Subgroup Separable and Weakly Potent Groups

We give a characterization of the cyclic subgroup separability and weak potency of the fundamental group of a graph of polycyclic-by-finite groups and free-by-finite groups amalgamating edge subgroups of the form × D,where h has infinite order and D is finite.     

On equivariant global epsilon constants for certain dihedral extensions

We consider a conjecture of Bley and Burns which relates the epsilon constant of the equivariant Artin -function of a Galois extension of number fields to certain natural algebraic invariants. For an odd prime number , we describe an algorithm which either proves the conjecture for all degree dihedral extensions of the rational numbers or finds a counterexample. We apply this to show the conjecture for all degree dihedral extensions of . The correctness of the algorithm follows from a finiteness property of the conjecture which we prove in full generality.

     

conjugacy of 1-d diffeomorphisms with periodic points

It is shown that the set of heteroclinic orbits between two periodic orbits of saddle-node type induces functional moduli which are completely contained in a new `transition map'. For one-dimensional diffeomorphisms with saddle-node periodic points, two such diffeomorphisms are conjugated if and only if the transition maps of their heteroclinic orbits are the same. An equivalent transition map is given for diffeomorphisms with hyperbolic periodic points, and it is shown that this transition map is an invariant of conjugation. However, in this case the transition map alone is sufficient to guarantee conjugacy only in a limited sense.

     

HNN extensions of von Neumann algebras

Reduced HNN extensions of von Neumann algebras (as well as C^*-algebras) will be introduced, and their modular theory, factoriality and ultraproducts will be discussed. In several concrete settings, detailed analysis on them will be also carried out.     

Structural interactions of conjugacy closed loops

We study conjugacy closed loops by means of their multiplication groups. Let be a conjugacy closed loop, its nucleus, the associator subloop, and and the left and right multiplication groups, respectively. Put . We prove that the cosets of agree with orbits of , that and that one can define an abelian group on . We also explain why the study of finite conjugacy closed loops can be restricted to the case of nilpotent. Group is shown to be a subgroup of a power of (which is abelian), and we prove that can be embedded into . Finally, we describe all conjugacy closed loops of order .

     

Morse theory and conjugacy classes of finite subgroups

We construct a CAT(0) group containing a finitely presented subgroup with infinitely many conjugacy classes of finite-order elements. Unlike previous examples (which were based on right-angled Artin groups) our ambient CAT(0) group does not contain any rank 3 free abelian subgroups. We also construct examples of groups of type F _n inside mapping class groups, Aut(), and Out() which have infinitely many conjugacy classes of finite-order elements.      

Unbounded extensions and operator moment problems

Extension results, expressed in terms of complete boundedness, leading to necessary and sufficient conditions for the solvability of power moment problems with unbounded operator data are given. As an application, necessary and sufficient conditions for the existence of selfadjoint and normal extensions for some classes of commuting tuples of unbounded linear operators are obtained.     

Groups with few conjugacy classes of non-normal subgroups

The structure of groups with finitely many non-normal subgroups is well known. In this paper, groups are investigated with finitely many conjugacy classes of non-normal subgroups with a given property. In particular, it is proved that a locally soluble group with finitely many non-trivial conjugacy classes of non-abelian subgroups has finite commutator subgroup. This result generalizes a theorem by Romalis and Sesekin on groups in which every non-abelian subgroup is normal.      

Atomic Properties of the Hawaiian Earring Group for HNN Extensions

In 2011, while investigating fundamental groups of wild spaces, K.Eda [7 Eda , K. ( 2011 ). Atomic property of the fundamental groups of the Hawaiian earring and wild locally path-connected spaces . Jour. Math. Soc. Japan 63 ( 3 ): 769 – 787 .[Crossref], [Web of Science ®] , [Google Scholar]] showed that the fundamental group of the Hawaiian earring (the Hawaiian earring group, in short) has the property that for any homomorphism h from it to a free product A*B, there exists a natural number N such that is contained in a conjugate subgroup to A or B. In the present article, we prove a corresponding property for certain HNN extensions and amalgamated free products. This allows us to show that some one-relator groups, including Baumslag–Solitar groups, are n-slender.     

Hochschild and Cyclic Homology of Ore Extensions and Some Examples of Quantum Algebras

For every Ore extension we construct a chain complex giving its Hochschild homology. As an application we compute the Hochschild and cyclic homology of an arbitrary multiparametric affine space and the Hochschild homology of the algebra of differential operators over this space, in the generic case.     

Intersections of conjugacy classes and subgroups of algebraic groups

We show that if is a reductive group, then th roots of conjugacy classes are a finite union of conjugacy classes, and that if is an algebraic overgroup of , then the intersection of with a conjugacy class of is a finite union of -conjugacy classes. These results follow from results on finiteness of unipotent classes in an almost simple algebraic group.

     

Embedding theorems for HNN extensions of inverse semigroups

A variant of an HNN extension of an inverse semigroup introduced by Gilbert [N.D. Gilbert, HNN extensions of inverse semigroups and groupoids, J. Algebra 272 (2004) 27-45] is defined provided that associated subsemigroups are order ideals. We show this presentation still makes sense without the assumption on associated subsemigroups in the sense that it gives a semigroup deserving to be an HNN extension, and it is embedded into another variant using the automata theoretical technique based on combinatorial and geometrical properties of Schützenberger graphs.