Riemann-Liouville operator in weighted \(L_p\) spaces via the Jacobi series expansion (Q2306356)

Summary: In this paper, we use the orthogonal system of the Jacobi polynomials as a tool to study the Riemann-Liouville fractional integral and derivative operators on a compact subset of the real axis. This approach has some advantages and allows us to complete the previously known results of the fractional calculus theory by means of reformulating them. The proved theorem on the fractional integral operator action is formulated in terms of the Jacobi series coefficients and is of particular interest. We obtain a sufficient condition for a representation of a function by the fractional integral in terms of the Jacobi series coefficients. We consider several modifications of the Jacobi polynomials, which gives us the opportunity to study the invariant property of the Riemann-Liouville operator. In this direction, we have shown that the fractional integral operator acting in the weighted spaces of Lebesgue square integrable functions has a sequence of included invariant subspaces.