Thin subbases of Piatetski-Shapiro sequences

Abstract

For a non-integral real number $c>1$, let ${\mathbb{N}}_{(c)}:=\{\lfloor n^c\rfloor |n\in \mathbb{N}\}$. We show that ${\mathbb{N}}_{(c)}$ contains thin subbases of every order $h\ge 5$ when $1<c<2$, and $h\ge (\lfloor 2c\rfloor +1)(\lfloor 2c\rfloor +2)+1$ when $c>2$. In fact, for every regularly varying function $F$ such that \[ \frac{F(x)}{\log x}\to\infty\quad\text{ and } \quad F(x)\leq (1+o(1))\frac{Γ(1+1/c)^h}{Γ(h/c)} x^{h/c-1}, \] there exists $A\subseteq {\mathbb{N}}_{(c)}$ with $r_{A,h}(n)\sim F(n)$. We also establish analogous results for $k$-th powers of Piatetski-Shapiro numbers and Piatetski-Shapiro primes for small $c$.

23 pages