The Equalizer Conjecture For The Free Group of Rank Two
Author(s) -
Alan D. Logan
Publication year - 2021
Publication title -
the quarterly journal of mathematics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.922
H-Index - 35
eISSN - 1464-3847
pISSN - 0033-5606
DOI - 10.1093/qmath/haab059
Subject(s) - injective function , homomorphism , rank (graph theory) , conjecture , mathematics , combinatorics , equalizer , group (periodic table) , finitely generated abelian group , invertible matrix , free group , discrete mathematics , pure mathematics , physics , computer science , channel (broadcasting) , telecommunications , quantum mechanics
The equalizer of a set of homomorphisms $S: F(a, b)\rightarrow F(\Delta)$ has rank at most two if S contains an injective map and is not finitely generated otherwise. This proves a strong form of Stallings’ Equalizer Conjecture for the free group of rank two. Results are also obtained for pairs of homomorphisms $g, h:F(\Sigma)\rightarrow F(\Delta)$ when the images are inert in, or retracts of, $F(\Delta)$.
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