Totally Lindelöf and totally ω-narrow paratopological groups

Generalized metric spaces with algebraic structures

Metrizability of paratopological (semitopological) groups

It is shown that if all countable subgroups of a semitopological group G are precompact, then G is also precompact and that the closure of an arbitrary subgroup of G is again a subgroup. We present a general method of refining the topology of a given commutative paratopological group G such that the group G with the finer topology, say, σ is again a paratopological group containing a subgroup whose closure in (G, σ) is not a subgroup. It is also proved that a feebly compact paratopological group H is perfectly k-normal and that every Gδ-dense subspace of H is feebly compact.

Given a T0 paratopological group G and a class C of continuous homomorphisms of paratopological groups, we define the C-semicompletionC[G) and C-completionC[G] of the group G that contain G as a dense subgroup, satisfy the T0-separation axiom and have certain universality properties. For special classes C, we present some necessary and sufficient conditions on G in order that the (semi)completions C[G) and C[G] be Hausdorff. Also, we give an example of a Hausdorff paratopological abelian group G whose C-semicompletion C[G) fails to be a T1-space, where C is the class of continuous homomorphisms of sequentially compact topological groups to paratopological groups. In particular, the group G contains an ω-bounded sequentially compact subgroup H such that H is a topological group but its closure in G fails to be a subgroup.

In this article, we introduce fuzzy paratopological group, fuzzy semitopological group and fuzzy quasitopological group with illustrative examples and properties. These new notions belong to fuzzy topological group. Here, we prove that each fuzzy regular paratopological group is completely regular by using fuzzy uniformities. Moreover, we prove some results related to fuzzy semitopological group and fuzzy quasitopological group. In addition, we provide an application in the area of decision making during robot crash by using our above stated notions and nano topology.

In this paper we consider two questions in the realm of paratopological groups: When does multiplication on a given Tychonoff paratopological group H admit an extension to continuous multiplication on the Dieudonne completion, \(\mu {H}\), of H in such a way that H turns into a dense subgroup of the paratopological group \(\mu {H}\)? and, if A and B are bounded subsets of paratopological groups G and H, respectively, is \(A\times B\) bounded in \(G\times H\)? The motivation for these questions comes from the field of topological groups and they are receiving a special attention as an interesting source of open problems.

In this chapter we introduce several most important notions and constructions concerning topological groups and operations with them. In particular, we develop the technique of prenorms on groups, describe in detail the construction of the Raĭkov completion of a topological group, prove a theorem on embeddings of topological groups into groups of isometries in the topology of pointwise convergence. We also introduce the class of locally compact topological groups and provide the reader with the first basic facts about groups in this class (deeper results in this direction will be presented in Chapter 9). Then we define and study the important classes of !-narrowtopological groups and of precompact (equivalently, totally bounded) topological groups. We finish this chapter with the Hartman{Mycielski construction of an embedding of an arbitrary topological group into a connected, locally pathwise connected topological group.

A now standard technique for treating a class of Baire set problems, originating with Halmos [2; 51.D], is to construct a metric space that, in a way, "fixes" a given Baire set. Formally this means, given a Baire set B in a space X, find a metric space M and a map g of X onto M with the property that B = g l gB . In phrasing the problem for topological groups it is natural to require that M be a group and g be a homomorphism. Specifically, what is desired is a subgroup H that "fixes" B, i.e., such that B = BH. This problem is solved in Halmos for locally compact a-compact groups in a theorem [2; 64.G] that has led to interesting consequences elsewhere [4, 1]. As will be seen, Halmos' theorem is also true for totally bounded groups. An example of Sirota's of a countable topological group with no non-trivial metrizable homomorphic images indicates that, in this direction at least, the barrier of local compactness cannot be lifted without giving up metrizability in M. If this is done, however, replacing the requirement that M be metrizable, i.e., that H have a countable base in G, with the less stringent requirement that H be a G~-set in G, an analogue of Halmos' theorem is true for Lindelff groups. In view of these remarks it is convenient to distinguish between two distinct Baire set fixing problems. A closed invariant subgroup H of a group G is said to be a fixiru3 subgroup (M-fixing subgroup) provided H is a G~-set (H has a countable base of neighborhoods in G). G satisfies the Baire set fixing property (M-Baire set fixing property) provided, for each Baire set in G, there is a fixing subgroup (M-fixing subgroup) such that B = BH. The Baire sets are taken to be the elements of the smallest a-algebra containing the zero sets of continuous real-valued functions on G. For technical convenience in describing proofs, a G~-set containing the identity is called an admissible set.

A study on weakly Lindelöf (para)topological groups with a q-point and m([formula omitted])-factorizability

We provide new arguments to see topological Kac-Moody groups as generalized semisimple groups over local fields: they are products of topologically simple groups and their Iwahori subgroups are the normalizers of the pro-p Sylow subgroups. We use a dynamical characterization of parabolic subgroups to prove that some countable Kac-Moody groups with Fuchsian buildings are not linear. We show for this that the linearity of a countable Kac-Moody group implies the existence of a closed embedding of the corresponding topological group in a non-Archimedean simple Lie group, thanks to a commensurator super-rigidity theorem proved in the Appendix by P. Bonvin.

A mapping f : G → s from a left topological group G into a semigroup S is a local homomorphism if for every x є G \ {e}, there is a neighborhood Ux of e such that f (xy) = f (x)f (y) for all y є Ux \ {e}. A local homomorphism f : G → S is onto if for every neighborhood U of e, f(U \ {e}) = S. We show that(1) every countable regular left topological group containing a discrete subset with exactly one accumulation point admits a local homomorphism onto N,(2) it is consistent that every countable topological group containing a discrete subset with exactly one accumulation point admits a local homomorphism onto any countable semigroup,(3) it is consistent that every countable nondiscrete maximally almost periodic topological group admits a local homomorphism onto the countably infinite right zero semigroup.

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Compactification of a space X is a compact space containing X as a dense subspace. Magills construction for compactications of a fixed Tychonoff space through partitions is applied to derive compactications of various Tychonoff spaces (X;T), with a fixed set X and with a variation in Tychonoff topologies 'T'. Some possible extensions of mappings are obtained in this regard. Magills construction for compactications of a fixed Tychonoff space through partitions is applied to derive compactications of various Tychonoff spaces (X;T), with a fixed set X and with a variation in Tychonoff topologies 'T'. Some possible extensions of mappings are obtained in this regard. In a compact extension of a topological group, the inverse operation should be extendable homeomorphically from the base topological group. Finally mappings are extended homeomorphically from topological space to its compact extension, when topologies are also varied.

Introduction to topological groups

We consider pointwise convergence in a separable Rosenthal compactum. The main result is that if $X \subset {{\mathbf {R}}^{{\omega ^\omega }}}$ is a Rosenthal compactum, $Y \subset X$ is countable dense and $x \in X$, then the following are equivalent: (i) $Y$ has a countable base at $x$. (ii) $\{ ({Y_i}) \in {Y^\omega }:{\lim _{i \to \infty }}{y_i} = x\}$ is analytic, when $Y$ has the discrete topology.