Understanding Schubert’s book. II. (English) Zbl 07560234

Summary: In this paper, we give rigorous justification of the ideas put forward in §20, Chapter 4 of Schubert’s book; a section that deals with the enumeration of conics in space. In that section, Schubert introduced two degenerate conditions about conics, i.e., the double line and the two intersection lines. Using these two degenerate conditions, he obtained all relations regarding the following three conditions: conics whose planes pass through a given point, conics intersecting with a given line, and conics which are tangent to a given plane. We use the language of blow-ups to rigorously treat the two degenerate conditions and prove all formulas about degenerate conditions stemming from Schubert’s idea.
For Part I, see [the author, ibid. 41, No. 1, 97–113 (2021; Zbl 07556683)].


14H50 Plane and space curves
14N15 Classical problems, Schubert calculus


Zbl 07556683
Full Text: DOI


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