Two-sided estimate for the modulus of continuity of a convolution

We study the differential properties of the convolution of functions with a generalized Bessel-Macdonald kernel. The integral properties of a function are characterized in terms of its decreasing permutation. The differential properties of the convolution are described in terms of its modulus of continuity of arbitrary order in the uniform norm. We obtain order-sharp estimates for the modulus of continuity of the convolution. By way of application, we present two-sided estimates for the modulus of continuity of the classical Bessel potential.