Linear dimension-free estimates for the Hermite-Riesz transforms

TL;DR

This paper proves dimension-free bounds for Hermite-Riesz transforms using Bellman functions, establishing new inequalities and spectral multiplier estimates that are independent of dimension and p, with potential applications to various differential operators.

Contribution

The paper introduces a novel Bellman function approach to obtain dimension-free inequalities for Hermite operators and Riesz transforms, extending to spectral multipliers and Schrödinger semigroups.

Findings

Dimension-free bilinear inequality for Hermite operator

Boundedness of Riesz-Hermite transforms on L^p with linear p dependence

L^p estimates for spectral multipliers independent of dimension

Abstract

We utilize the Bellman function technique to prove a bilinear dimension-free inequality for the Hermite operator. The Bellman technique is applied here to a non-local operator, which at first did not seem to be feasible. As a consequence of our bilinear inequality one proves dimension-free boundedness for the Riesz-Hermite transforms on L^p with linear growth in terms of p. A feature of the proof is a theorem establishing L^p(R^n) estimates for a class of spectral multipliers with bounds independent of n and p. Connections with known results on the Heisenberg group as well as with results for the Hilbert transform along the parabola are also explored. We believe our approach is quite universal in the sense that one could apply it to a whole range of Riesz transforms arising from various differential operators. As a first step towards this goal we prove our dimension-free bilinear embedding theorem for quite a general family of Schroedinger semigroups.