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Affine Lines on Affine Surfaces and the Makar–Limanov Invariant

Published online by Cambridge University Press:  20 November 2018

R. V. Gurjar
Affiliation:
School of Mathematics, Tata Institute for Fundamental Research, Homi Bhabha Road, Mumbai 400005, India e-mail: gurjar@math.tifr.res.in
K. Masuda
Affiliation:
Graduate School of Material Sciences, University of Hyogo, Himeji 671-2201, Japan e-mail: kayo@sci.u-hyogo.ac.jp
M. Miyanishi
Affiliation:
School of Science and Technology, Kwansei Gakuin University, Hyogo 669-1337, Japan e-mail: miyanisi@ksc.kwansei.ac.jp
P. Russell
Affiliation:
Department of Mathematics and Statistics, McGill University, Montreal, QC, H3A 2K6 e-mail: russell@math.mcgill.ca
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Abstract

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A smooth affine surface $X$ defined over the complex field $\mathbb{C}$ is an $\text{M}{{\text{L}}_{0}}$ surface if the Makar–Limanov invariant $\text{ML(}X\text{)}$ is trivial. In this paper we study the topology and geometry of $\text{M}{{\text{L}}_{0}}$ surfaces. Of particular interest is the question: Is every curve $C$ in $X$ which is isomorphic to the affine line a fiber component of an ${{\mathbb{A}}^{1}}$-fibration on $X$? We shall show that the answer is affirmative if the Picard number $\rho (X)\,=\,0$, but negative in case $\rho (X)\,\ge \,1$. We shall also study the ascent and descent of the $\text{M}{{\text{L}}_{0}}$ property under proper maps.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 2008

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