© The London Mathematical Society
Subspace Arrangements Defined by Products of Linear Forms
Department of Mathematics, Royal Institute of Technology S-100 44 Stockholm, Sweden bjorner{at}math.kth.se
Department of Mathematics, Cornell University Ithaca, NY 14853, USA irena{at}math.cornell.edu
Department of Mathematics and Statistics, 415 A Clapp Lab, Mount Holyoke College South Hadley, MA 01075, USA jsidman{at}mtholyoke.edu
Received 27 January 2004.
The vanishing ideal of an arrangement of linear subspaces in a vector space is considered, and the paper investigates when this ideal can be generated by products of linear forms. A combinatorial construction (blocker duality) is introduced which yields such generators in cases with a great deal of combinatorial structure, and examples are presented that inspired the work. A construction is given which produces all elements of this type in the vanishing ideal of the arrangement. This leads to an algorithm for deciding if the ideal is generated by products of linear forms. Generic arrangements of points in P2 and lines in P3 are also considered.