We define the Heisenberg Kakeya maximal functions Mδf, 0<δ<1, by averaging over δ-neighborhoods of horizontal unit line segments in the Heisenberg group H1
Nearby in the stack
equipped with the Korányi distance
dH
. We show that
∥Mδf∥L3(S1)≤C(ε)δ−1/3−ε∥f∥L3(H1),f∈L3(H1),
for all
ε>0
. The proof is based on a recent variant, due to Pramanik, Yang, and Zahl, of Wolff's circular maximal function theorem for a class of planar curves related to Sogge's cinematic curvature condition. As an application of our Kakeya maximal inequality, we recover the sharp lower bound for the Hausdorff dimension of Heisenberg Kakeya sets of horizontal unit line segments in