Extrapolations on ball Banach function spaces and applications

In this paper, some extrapolations on ball Banach function spaces are established. As applications, we obtain the boundedness of fractional spherical maximal operators, fractional integral operators with rough kernels, spherical maximal operators, strongly singular integral operators and maximal Bochner–Riesz operators on ball Banach function spaces. Finally, we apply these boundedness results to two concrete examples of ball Banach function spaces, namely, variable Lebesgue spaces and mixed-norm Lebesgue spaces.