English

On a continuation of quaternionic and octonionic logarithm along curves and the winding number

Complex Variables 2024-03-08 v1

Abstract

This paper focuses on the problem of finding a continuous extension of the hypercomplex logarithm along a path. While a branch of the complex logarithm can be defined in a small open neighbourhood of a strictly negative real point, no continuous branch of the hypercomplex logarithm can be defined in any open set AK{0}A\subset \mathbb K\setminus \{0\} which contains a strictly negative real point x0x_0 (here K\mathbb K represents the algebra of quaternions or octonions). To overcome these difficulties, we introduced the logarithmic manifold EK+\mathscr E_\mathbb K^+ and then showed that if qK, q=x+Iyq\in\mathbb K,\ q=x+Iy then E(x+Iy)E(x+Iy) %= (\exp (x + Iy), Iy) = (\exp x \cos y + I\exp x \sin y, Iy) is an immersion and a diffeomorphism between K\mathbb K and EK+\mathscr E_\mathbb K^+. In this paper, we consider lifts of paths in K{0}\mathbb K\setminus\{0\} to the logarithmic manifold EK+\mathscr{E}^+_\mathbb K; even though K{0}\mathbb K \setminus \{0\} is simply connected, in general, given a path in K{0}\mathbb K \setminus \{0\}, the existence of a lift of this path to EK+\mathscr{E}^+_\mathbb K is not guaranteed. There is an obvious equivalence between the problem of lifting a path in K{0}\mathbb K \setminus \{0\} and the one of finding a continuation of the hypercomplex logarithm logK\log_{\mathbb K} along this path.

Keywords

Cite

@article{arxiv.2307.14047,
  title  = {On a continuation of quaternionic and octonionic logarithm along curves and the winding number},
  author = {Graziano Gentili and Jasna Prezelj and Fabio Vlacci},
  journal= {arXiv preprint arXiv:2307.14047},
  year   = {2024}
}

Comments

30 pages, 4 figures