Companion Matrix for Composition of Polynomials and Its Application to Knot Theory
摘要
Abstract
A new formula is given for the companion matrix of the composition of two polynomials over a commutative ring. The results obtained are used to provide a constructive proof of Plans’ theorem for 2-bridge knots, which states that the first homology group of an odd-fold cyclic covering of a three-dimensional sphere branched over a given knot is the direct sum of two copies of some Abelian group. A similar result is also true for the homology of even-fold coverings factored by the reduced homology group of two-fold coverings. The structure of the above-mentioned Abelian groups is described through Chebyshev polynomials of the second and fourth kinds.