New results of Bollobás-type theorem for affine subspaces and projective subspaces

Abstract

Bollobás-type theorem has received a lot of attention due to its application in graph theory. In 2015, Gábor Heged{ü}s gave an upper bound of bollobás-type affine subspace families for $q\ne 2$, and constructed an almost sharp affine subspaces pair families. In this note, we prove a new upper bound for bollobás-type affine subspaces without the requirement of $q\ne 2$, and construct a pair of families of affine subspaces, which shows that our upper bound is sharp. We also give an upper bound for bollobás-type projective subspaces, and prove that the Heged{ü}s's conjecture holds when $q=2$.

6 pages