English

On the topology of free paratopological groups. II

General Topology 2013-01-15 v3

Abstract

Let \FP(X)\FP(X) be the free paratopological group on a topological space XX. For nNn\in \N, denote by \FPn(X)\FP_n(X) the subset of \FP(X)\FP(X) consisting of all words of reduced length at most nn, and by ini_n the natural mapping from (XX1{e})n(X\oplus X^{-1}\oplus \{e\})^n to \FPn(X)\FP_n(X). In this paper a neighbourhood base at the identity ee in \FP2(X)\FP_2(X) is found. A number of characterisations are then given of the circumstances under which i2 ⁣:(XXd1{e})2\FP2(X)i_2\colon (X\oplus X^{-1}_d\oplus \{e\})^2\to \FP_2(X) is a quotient map, where XX is a T1T_1 space and Xd1X^{-1}_d denotes the set X1X^{-1} equipped with the discrete topology. Further characterisations are given in the case where XX is a transitive T1T_1 space. Several specific spaces and classes of spaces are also examined. For example, i2i_2 is a quotient for every countable subspace of R\R, i2i_2 is not a quotient for any uncountable compact subspace of R\R, and it is undecidable in ZFC whether an uncountable subspace of R\R exists for which i2i_2 is a quotient.

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Cite

@article{arxiv.1206.5949,
  title  = {On the topology of free paratopological groups. II},
  author = {Ali Sayed Elfard and Peter Nickolas},
  journal= {arXiv preprint arXiv:1206.5949},
  year   = {2013}
}

Comments

This paper has been published by Topology and its Applications