2019/08/27 by Dougherty, Michael, McCammond, Jon · 1 citation
#30C10 #30C15 (Primary) 05A10 #57N80 (Secondary) #Combinatorics (math.CO) #Complex Variables (math.CV) #FOS: Mathematics #Geometric Topology (math.GT)
paper · doi:10.48550/arxiv.1908.10477
Given any n-tuple of complex numbers, one can canonically define a polynomial of degree n+1 that has the entries of this n-tuple as its critical points. In 2002, Beardon, Carne, and Ng studied a map θ\colon ℂn→ ℂn which outputs the critical values of the canonical polynomial constructed from the input, and they proved that this map is onto. Along the way, they showed that θ is a local homeomorphism whenever the entries of the input are distinct and nonzero, and, implicitly, they produced a polynomial expression for the Jacobian determinant of θ. In this article we extend and generalize both the local homeomorphism result and the elegant determinant identity to analogous situations where the critical points occur with multiplicities. This involves stratifying ℂn according to which coordinates are equal and generalizing θ to a similar map ℂ^ℓ → ℂ^ℓ where ℓ is the number of distinct critical points. The more complicated determinant identity that we establish is closely connected to the multinomial identity known as Dyson's conjecture.