English

Diffeomorphisms of the closed unit disc converging to the identity

General Mathematics 2017-07-12 v1

Abstract

If G\mathcal{G} is the group (under composition) of diffeomorphisms f:Dˉ(0;1)Dˉ(0;1)f : {\bar{D}}(0;1) \rightarrow {\bar{D}}(0;1) of the closed unit disc Dˉ(0;1){\bar{D}}(0;1) which are the identity map id:Dˉ(0;1)Dˉ(0;1)id : {\bar{D}}(0;1) \rightarrow {\bar{D}}(0;1) on the closed unit circle and satisfy the condition det(J(f))>0det(J(f)) > 0, where J(f)J(f) is the Jacobian matrix of ff or (equivalently) the Fr\'echet derivative of ff, then G\mathcal{G} equipped with the metric dG(f,g)=fg+J(f)J(g)d_{\mathcal{G}}(f,g) = \Vert f-g \Vert_{\infty } + \Vert J(f) - J(g) \Vert_{\infty }, where ff, gg range over G\mathcal{G}, is a metric space in which dG(ft,id)0d_{\mathcal{G}} \left( f_{t} , id \right) \rightarrow 0 as t1+t \rightarrow 1^{+}, where ft(z)=tz1+(t1)zf_{t}(z) = \frac{ tz }{ 1 + (t-1) \vert z \vert }, whenever zDˉ(0;1)z \in {\bar{D}}(0;1) and t1t \geq 1.

Keywords

Cite

@article{arxiv.1707.03293,
  title  = {Diffeomorphisms of the closed unit disc converging to the identity},
  author = {Nikolaos E. Sofronidis},
  journal= {arXiv preprint arXiv:1707.03293},
  year   = {2017}
}