English

Liouville's Theorem on integration in finite terms for $\mathrm D_\infty,$ $ \mathrm{SL}_2$ and Weierstrass field extensions

Classical Analysis and ODEs 2023-08-02 v1

Abstract

Let kk be a differential field of characteristic zero and the field of constants CC of kk be an algebraically closed field. Let EE be a differential field extension of kk having CC as its field of constants and that E=EmEm1E1E0=k,E=E_m\supseteq E_{m-1}\supseteq\cdots\supseteq E_1\supseteq E_0=k, where EiE_i is either an elementary extension of Ei1E_{i-1} or Ei=Ei1(ti,ti)E_i=E_{i-1}(t_i, t'_i) and tit_i is weierstrassian (in the sense of Kolchin ([Page 803, Kolchin1953]) over Ei1E_{i-1} or EiE_i is a Picard-Vessiot extension of Ei1E_{i-1} having a differential Galois group isomorphic to either the special linear group SL2(C)\mathrm{SL}_2(C) or the infinite dihedral subgroup D\mathrm{D}_\infty of SL2(C).\mathrm{SL}_2(C). In this article, we prove that Liouville's theorem on integration in finite terms ([Theorem, Rosenlicht1968]) holds for EE. That is, if ηE\eta\in E and ηk\eta'\in k then there is a positive integer nn and for i=1,2,,n,i=1,2,\dots,n, there are elements ciC,c_i\in C, uik{0}u_i\in k\setminus \{0\} and vkv\in k such that η=i=1nciuiui+v.\eta'=\sum^n_{i=1}c_i\frac{u'_i}{u_i}+v'.

Keywords

Cite

@article{arxiv.2308.00659,
  title  = {Liouville's Theorem on integration in finite terms for $\mathrm D_\infty,$ $ \mathrm{SL}_2$ and Weierstrass field extensions},
  author = {Partha Kumbhakar and Varadharaj R. Srinivasan},
  journal= {arXiv preprint arXiv:2308.00659},
  year   = {2023}
}

Comments

10 pages, accepted for a publication at archiv der mathematik