On Fulton’s Algorithm for Computing Intersection Multiplicities

  • Steffen Marcus
  • Marc Moreno Maza
  • Paul Vrbik
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 7442)


As pointed out by Fulton in his Intersection Theory, the intersection multiplicities of two plane curves V(f) and V(g) satisfy a series of 7 properties which uniquely define I(p;f,g) at each point p ∈ V(f,g). Moreover, the proof of this remarkable fact is constructive, which leads to an algorithm, that we call Fulton’s Algorithm. This construction, however, does not generalize to n polynomials f 1, …, f n . Another practical limitation, when targeting a computer implementation, is the fact that the coordinates of the point p must be in the field of the coefficients of f 1, …, f n . In this paper, we adapt Fulton’s Algorithm such that it can work at any point of V(f,g), rational or not. In addition, we propose algorithmic criteria for reducing the case of n variables to the bivariate one. Experimental results are also reported.


Maximal Ideal Tangent Cone Polynomial System Bivariate Case Tangent Hyperplane 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Steffen Marcus
    • 1
  • Marc Moreno Maza
    • 2
  • Paul Vrbik
    • 2
  1. 1.Department of MathematicsUniversity of UtahUSA
  2. 2.Department of Computer ScienceUniversity of Western OntarioCanada

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