English

Holomorphic fundamental semigroup of Riemann domains

Complex Variables 2017-08-15 v3

Abstract

Let (W,Π)(W,\Pi) be a Riemann domain over a complex manifold MM and w0w_0 be a point in WW. Let D\mathbb D be the unit disk in C\mathbb C and T=\bdD\mathbb T=\bd\mathbb D. Consider the space S1,w0(Dˉ,W,M){\mathcal S}_{1,w_0}({\bar{\mathbb D}},W,M) of continuous mappings ff of T\mathbb T into WW such that f(1)=w0f(1)=w_0 and Πf\Pi\circ f extends to a holomorphic on D\mathbb D mapping f^\hat f. Mappings f0,f1S1,w0(Dˉ,W,M)f_0,f_1\in{\mathcal S}_{1,w_0}({\bar{\mathbb D}},W,M) are called {\it hh-homotopic} if there is a continuous mapping ftf_t of [0,1][0,1] into \rS1,w0(Dˉ,W,M)\rS_{1,w_0}({\bar{\mathbb D}},W,M). Clearly, the hh-homotopy is an equivalence relation and the equivalence class of fS1,w0(Dˉ,W,M)f\in{\mathcal S}_{1,w_0}({\bar{\mathbb D}},W,M) will be denoted by [f][f] and the set of all equivalence classes by η1(W,M,w0)\eta_1(W,M,w_0). There is a natural mapping ι1:η1(W,M,w0)π1(W,w0)\iota_1:\,\eta_1(W,M,w_0)\to\pi_1(W,w_0) generated by assigning to fS1,w0(Dˉ,W,M)f\in{\mathcal S}_{1,w_0}({\bar{\mathbb D}},W,M) its restriction to T\mathbb T. We introduce on η1(W,M,w0)\eta_1(W,M,w_0) a binary operation \star which induces on η1(W,M,w0)\eta_1(W,M,w_0) a structure of a semigroup with unity. Moreover, ι1([f1][f2])=ι1([f1])ι1([f2])\iota_1([f_1]\star[f_2])=\iota_1([f_1])\cdot\iota_1([f_2]), where \cdot is the standard operation on π1(W,w0)\pi_1(W,w_0). Then we establish standard properties of η1(W,M,w0)\eta_1(W,M,w_0) and provide some examples. In particular, we completely describe η1(W,M,w0)\eta_1(W,M,w_0) when WW is a finitely connected domain in M=CM=\mathbb C and Π\Pi is an identity. In particular, we show for a general domain W\mahbbCW\subset\mahbb C that [f1]=[f2][f_1]=[f_2] if and only if ι1([f1])=ι1([f2])\iota_1([f_1])=\iota_1([f_2]).

Keywords

Cite

@article{arxiv.1210.1191,
  title  = {Holomorphic fundamental semigroup of Riemann domains},
  author = {Dayal Dharmasena and Evgeny A. Poletsky},
  journal= {arXiv preprint arXiv:1210.1191},
  year   = {2017}
}

Comments

The paper was drastically reworked and corrected and got the new title