A one parameter family of Volterra-type operators

TL;DR

This paper investigates the properties of a family of Volterra-type operators parameterized by lpha, focusing on their norms, spectra, eigenfunctions, and iterates within various L^p spaces, including the case p=q=2.

Contribution

It provides explicit calculations of norms, spectra, and eigenfunctions for the operators T_lpha and their compositions, extending understanding of their functional analysis properties.

Findings

Explicit formulas for operator norms across p, q.

Spectral analysis of T_lpha and T_lpha^* T_lpha.

Characterization of eigenfunctions and spectra for specific cases.

Abstract

For every $\alpha \in (0,+\infty)$ and $p,q \in (1,+\infty)$ let $T_\alpha$ be the operator $L^p[0,1]\to L^q[0,1]$ defined via the equality $(T_\alpha f)(x) := \int_0^{x^\alpha} f(y) d y$. We study the norms of $T_\alpha$ for every $p$, $q$. In the case $p=q$ we further study its spectrum, point spectrum, eigenfunctions, and the norms of its iterates. Moreover, for the case $p=q=2$ we determine the point spectrum and eigenfunctions for $T^*_\alpha T_\alpha$, where $T^*_\alpha$ is the adjoint operator.