The Origins of Complex Geometry in the 19th Century ∗ Raymond O. Wells, Jr. y April 20, 2015 Contents 1 Introduction 1 2 The Complex Plane 4 3 Abel's Theorem 10 4 Elliptic Functions 21 5 Holomorphic functions and mappings 33 6 Riemann surfaces 54 7 Conclusion 69 1 Introduction One of the most beautiful and profound developments in the 19th century is complex geometry. We mean by this a constellation of discoveries that led to the modern theory of complex manifolds (and more generally complex spaces: complex manifolds with specified types of singularities) and modern algebraic geometry, both of which have played an important role in the 20th century. The arXiv:1504.04405v1 [math.HO] 16 Apr 2015 primary aspects to the theory of complex manifolds are the geometric structure itself, its topological structure, coordinate systems, etc., and holomorphic func- tions and mappings and their properties. Algebraic geometry over the complex number field uses polynomial and rational functions of complex variables as the primary tools, but the underlying topological structures are similar to those that appear in complex manifold theory, and the nature of singularities in both ∗The author would like to thank Howard Resnikoff for his careful reading and comments on an earlier draft of this paper yJacobs University Bremen; University of Colorado at Boulder;
[email protected] 1 the analytic and algebraic settings are also structurally very similar. Algebraic geometry uses the geometric intuition which arises from looking at varieties over the the complex and real case to deduce important results in arithmetic algebraic geometry where the complex number field is replaced by the field of rational numbers or various finite number fields.