Fractional powers of first order differential operators and new families of polynomials associated to inverse measures

TL;DR

This paper develops the theory of fractional powers of first order differential operators with zero order terms, explores associated fractional Sobolev spaces, and introduces new polynomial families linked to inverse measures like the inverse Gaussian.

Contribution

It establishes a comprehensive framework for fractional differential operators with inverse measures and introduces new polynomial families with their properties and applications.

Findings

Fractional powers of differential operators are characterized in inverse measure contexts.

New polynomial families related to inverse Gaussian, Laguerre, and Jacobi measures are introduced.

Boundedness of key singular integral operators in inverse measure settings is proven.

Abstract

First, we establish the theory of fractional powers of first order differential operators with zero order terms, obtaining PDE properties and analyzing the corresponding fractional Sobolev spaces. In particular, our study shows that Lebesgue and Sobolev spaces with inverse measures (like the inverse Gaussian measure) play a fundamental role in the theory of fractional powers of the first order operators. Second, and motivated in part by such a theory, we lay out the foundations for the development of the harmonic analysis for \emph{inverse} measures. We discover new families of polynomials related to the inverse Gaussian, Laguerre, and Jacobi measures, and characterize them using generating and Rodrigues formulas, and three-term recurrence relations. Moreover, we prove boundedness of several fundamental singular integral operators in these inverse measure settings.