Spectral multipliers on 2-step groups: topological versus homogeneous dimension

On the L2 → L∞ norms of spectral multipliers of “quasi- homogeneous” operators on homogeneous groups

We study the L2 → L∞ norms of spectral projections and spectral multipliers of left-invariant elliptic and subelliptic second-order differential operators on homogeneous Lie groups. We obtain a precise description of the L2 → L∞ norms of spectral multipliers for some class of operators which we call quasi-homogeneous. As an application we prove a stronger version of Alexopoulos’ spectral multip...

On Schur Multipliers of Pairs and Triples of Groups with Topological Approach

In this paper, using a relation between Schur multipliers of pairs and triples of groups, the fundamental group and homology groups of a homotopy pushout of Eilenberg-MacLane spaces, we present among other things some behaviors of Schur multipliers of pairs and triples with respect to free, amalgamated free, and direct products and also direct limits of groups with topological approach.

Ü Bounds for Spectral Multipliers on Nilpotent Groups

A criterion is given for the Lp boundedness of a class of spectral multiplier operators associated to left-invariant, homogeneous subelliptic second-order differential operators on nilpotent Lie groups, generalizing a theorem of Hörmander for radial Fourier multipliers on Euclidean space. The order of differentiability required is half the homogeneous dimension of the group, improving previous ...

Chapter 21 Problems on Topological Groups and Other Homogeneous Spaces

Double Multipliers on Topological Algebras

The main purpose of this paper is to investigate some topological properties of the double multiplier algebra on a topological algebra. Let Md(A) be the double multiplier algebra on a topological algebra A, and let u and s be the uniform and strong operator topologies on Md(A), respectively. It is shown, under some additional hypotheses on A, that (1) Md(A) is uand s-complete; (2) A is a u-clos...