English

Cycles of arbitrary length in distance graphs on $\mathbb{F}_q^d$

Combinatorics 2021-01-05 v1

Abstract

For EFqdE \subset {\Bbb F}_q^d, d2d \ge 2, where Fq{\Bbb F}_q is the finite field with qq elements, we consider the distance graph Gtdist(E){\mathcal G}^{dist}_t(E), t0t \not=0, where the vertices are the elements of EE, and two vertices xx, yy are connected by an edge if xy(x1y1)2++(xdyd)2=t||x-y|| \equiv {(x_1-y_1)}^2+\dots+{(x_d-y_d)}^2=t. We prove that if ECkqd+22|E| \ge C_k q^{\frac{d+2}{2}}, then Gtdist(E){\mathcal G}^{dist}_t(E) contains a statistically correct number of cycles of length kk. We are also going to consider the dot-product graph Gtprod(E){\mathcal G}^{prod}_t(E), t0t \not=0, where the vertices are the elements of EE, and two vertices xx, yy are connected by an edge if xyx1y1++xdyd=tx \cdot y \equiv x_1y_1+\dots+x_dy_d=t. We obtain similar results in this case using more sophisticated methods necessitated by the fact that the function xyx \cdot y is not translation invariant. The exponent d+22\frac{d+2}{2} is improved for sufficiently long cycles.

Keywords

Cite

@article{arxiv.2101.00748,
  title  = {Cycles of arbitrary length in distance graphs on $\mathbb{F}_q^d$},
  author = {Alex Iosevich and Gail Jardine and Brian McDonald},
  journal= {arXiv preprint arXiv:2101.00748},
  year   = {2021}
}