J. Aust. Math. Soc. 83 (2007), no. 1, pp. 135–148.

Local homomorphisms of topological groups

Yevhen Zelenyuk
School of Mathematics
University of the Witwatersrand
Private Bag 3
Wits 2050
South Africa
Received 21 November 2005; revised 31 May 2006
Communicated by G. Willis


A mapping f:G\to S from a left topological group G into a semigroup S is a local homomorphism if for every x\in G\setminus \{e\}, there is a neighborhood U_x of e such that f(xy)=f(x)f(y) for all y\in U_x\setminus \{e\}. A local homomorphism f:G\to S is onto if for every neighborhood U of e, f(U\setminus \{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 \mathbb {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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2000 Mathematics Subject Classification: primary 22A30, 54H11; secondary 54A35, 54G05
(Metadata: XML, RSS, BibTeX) MathSciNet: MR2354??? Z'blatt-MATH: pre05231337


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