On Jones' subgroup of R. Thompson group F

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• 作者：Gili Golan¹ ; ^{gili.golan@math.biu.ac.il" class="auth_mail" title="E-mail the corresponding author} ; Mark Sapir ; ² ; ^{m.sapir@vanderbilt.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：R. Thompson group ; Diagram groups ; Tree-diagrams ; Knots and links
• 刊名：Journal of Algebra
• 出版年：2017
• 出版时间：15 January 2017
• 年：2017
• 卷：470
• 期：Complete
• 页码：122-159
• 全文大小：1853 K

文摘

Recently Vaughan Jones showed that the R. Thompson group F   encodes in a natural way all knots and links in k to view the MathML source">R³, and a certain subgroup $\overrightarrow{F}$ of F   encodes all oriented knots and links. We answer several questions of Jones about $\overrightarrow{F}$. In particular we prove that the subgroup $\overrightarrow{F}$ is generated by k to view the MathML source">x₀x₁$x_0{x}_1$, k to view the MathML source">x₁x₂$x_1{x}_2$, k to view the MathML source">x₂x₃$x_2{x}_3$ (where k to view the MathML source">x_i$x_i$, k to view the MathML source">i∈N are the standard generators of F  ) and is isomorphic to k to view the MathML source">F₃$F_3$, the analog of F   where all slopes are powers of 3 and break points are 3-adic rationals. We also show that $\overrightarrow{F}$ coincides with its commensurator. Hence the linearization of the permutational representation of F   on $F/\overrightarrow{F}$ is irreducible. We show how to replace 3 in the above results by an arbitrary n, and to construct a series of irreducible representations of F defined in a similar way. Finally we analyze Jones' construction and deduce that the Thompson index of a link is linearly bounded in terms of the number of crossings in a link diagram.