The point counting problem in representation varieties of torus knots

Abstract

We compute the motive of the variety of representations of the torus knot of type (m,n) into the affine groups $AG{L}_1$ and $AG{L}_2$ for an arbitrary field $k$. In the case that $k=F_q$ is a finite field this gives rise to the count of the number of points of the representation variety, while for $k=C$ this calculation returns the E-polynomial of the representation variety. We discuss the interplay between these two results in sight of Katz theorem that relates the point count polynomial with the E-polynomial. In particular, we shall show that several point count polynomials exist for these representation varieties, depending on the arithmetic between m,n and the characteristic of the field, whereas only one of them agrees with the actual E-polynomial.

20 pages, 4 figures. arXiv admin note: text overlap with arXiv:2104.13651

References in corpus (1)

• On the E-polynomials of a family of Character Varieties