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Hardy Inequalities on Homogeneous Groups

100 Years of Hardy Inequalities

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This open access book provides an extensive treatment of Hardy inequalities and closely related topics from the point of view of Folland and Stein's homogeneous (Lie) groups. The place where Hardy inequalities and homogeneous groups meet is a beautiful area of mathematics with links to many other subjects. While describing the general theory of Hardy, Rellich, Caffarelli-Kohn-Nirenberg, Sobolev, and other inequalities in the setting of general homogeneous groups, the authors pay particular attention to the special class of stratified groups. In this environment, the theory of Hardy inequalities becomes intricately intertwined with the properties of sub-Laplacians and subelliptic partial differential equations. These topics constitute the core of this book and they are complemented by additional, closely related topics such as uncertainty principles, function spaces on homogeneous groups, the potential theory for stratified groups, and the potential theory for general Hörmander's sums of squares and their fundamental solutions.

This monograph is the winner of the 2018 Ferran Sunyer i Balaguer Prize, a prestigious award for books of expository nature presenting the latest developments in an active area of research in mathematics. As can be attested as the winner of such an award, it is a vital contribution to literature of analysis not only because it presents a detailed account of the recent developments in the field, but also because the book is accessible to anyone with a basic level of understanding of analysis. Undergraduate and graduate students as well as researchers from any field of mathematical and physical sciences related to analysis involving functional inequalities or analysis of homogeneous groups will find the text beneficial to deepen their understanding.

Inhaltsverzeichnis

Frontmatter

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Introduction
Abstract
The present book is devoted to the exposition of the research developments at the intersection of two active fields of mathematics: Hardy inequalities and related analysis, and the noncommutative analysis in the setting of nilpotent Lie groups of different types. Both subjects are very broad and deserve separate monograph presentations on their own, and many good books are already available.
Michael Ruzhansky, Durvudkhan Suragan

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Chapter 1 Analysis on Homogeneous Groups
Abstract
In this chapter we provide preliminaries for the analysis on homogeneous groups to make the use of the monograph more self-sufficient. We make a selection of topics which will be playing a role in the subsequent analysis. Thus, we first discuss relevant properties of general Lie groups and algebras and then concentrate on properties of homogeneous groups required for our further analysis. Lastly, we introduce the notion of the Euler operator on homogeneous groups and establish its main properties.
Michael Ruzhansky, Durvudkhan Suragan

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Chapter 2 Hardy Inequalities on Homogeneous Groups
Abstract
This chapter is devoted to Hardy inequalities and the analysis of their remainders in different forms. Moreover, we discuss several related inequalities such as Rellich inequalities and uncertainty principles.
Michael Ruzhansky, Durvudkhan Suragan

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Chapter 3 Rellich, Caffarelli–Kohn–Nirenberg, and Sobolev Type Inequalities
Abstract
This chapter is devoted to other functional inequalities usually associated to the Hardy inequalities. These include Rellich and Caffarell–Kohn–Nirenberg inequalities. We also discuss different aspects of this analysis such as their stability, higherorder inequalities, their weighted and extended versions.
Michael Ruzhansky, Durvudkhan Suragan

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Chapter 4 Fractional Hardy Inequalities
Abstract
In this chapter we present results concerning fractional forms of Hardy inequalities. Such a topic is well investigated in the Abelian Euclidean setting and we will be providing relevant references in the sequel. For a general survey of fractional Laplacians in the Euclidean setting see, e.g., [Gar17]. However, as usual, the general approach based on homogeneous groups allows one to get insights also in the Abelian case, for example, from the point of view of the possibility of choosing an arbitrary quasi-norm. Moreover, another application of the setting of homogeneous groups is that the results can be equally applied to both elliptic and subelliptic problems.
Michael Ruzhansky, Durvudkhan Suragan

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Chapter 5 Integral Hardy Inequalities on Homogeneous Groups
Abstract
In this chapter we discuss the integral form of Hardy inequalities where instead of estimating a function by its gradient, we estimate the integral by the function itself.
Michael Ruzhansky, Durvudkhan Suragan

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Chapter 6 Horizontal Inequalities on Stratified Groups
Abstract
In this chapter we discuss versions of some of the inequalities from the previous chapters in the setting of stratified groups. Because of the stratified structure here we can use the horizontal gradient in the estimates.
Michael Ruzhansky, Durvudkhan Suragan

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Chapter 7 Hardy–Rellich Inequalities and Fundamental Solutions
Abstract
In this chapter, we describe the Hardy and other inequalities on stratified groups with the \(\mathcal{L}\)-gauge weights. The appearance of such weights has been discussed in the beginning of Chapter 6. The literature on inequalities with such weights is rather substantial. Apart from describing new results and methods we will be making relevant references to the results existing in the earlier literature.
Michael Ruzhansky, Durvudkhan Suragan

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Chapter 8 Geometric Hardy Inequalities on Stratified Groups
Abstract
Given a domain in the space, the ‘geometric’ version of Hardy inequalities usually refers to the Hardy type inequalities where the weight is given in terms of the distance to the boundary of the domain. In this chapter we discuss L2 and Lp versions of the geometric Hardy inequality on the stratified group \(\mathbb{G}\). For the clarity of the exposition, we first deal with the half-space domains, and then with more general convex domains.
Michael Ruzhansky, Durvudkhan Suragan

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Chapter 9 Uncertainty Relations on Homogeneous Groups
Abstract
In this chapter we discuss relations between main operators of quantum mechanics, that is, relations between momentum and position operators as well as Euler and Coulomb potential operators on homogeneous groups as well as their consequences. Since in most uncertainty relations and in these operators the appearing weights are radially symmetric, it turns out that these relations can be extended to also hold on general homogeneous groups. In particular, we obtain both isotropic and anisotropic uncertainty principles in a refined form, where the radial derivative operators are used instead of the elliptic or hypoelliptic differential operators.
Michael Ruzhansky, Durvudkhan Suragan

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Chapter 10 Function Spaces on Homogeneous Groups
Abstract
In this chapter, we describe several function spaces on homogeneous groups. The origins of the extensive use of homogeneous groups in analysis go back to the book [FS82] of Folland and Stein where Hardy spaces on homogeneous groups have been thoroughly analysed. It turns out that several other function spaces can be defined on homogeneous groups since their main structural properties essentially depend only on the group and dilation structures. Thus, in this chapter we carry out such a construction for Morrey and Campanato spaces and analyse their main properties. Moreover, we describe a version of Sobolev spaces associated to the Euler operator. We call such spaces the Euler–Hilbert–Sobolev spaces.
Michael Ruzhansky, Durvudkhan Suragan

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Chapter 11 Elements of Potential Theory on Stratified Groups
Abstract
In this chapter, we discuss elements of the potential theory and the theory of boundary layer operators in the setting of stratified groups. The main tools for this analysis are the fundamental solution for the sub-Laplacian and Green’s identities established in Section 1.4.4.
Michael Ruzhansky, Durvudkhan Suragan

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Chapter 12 Hardy and Rellich Inequalities for Sums of Squares of Vector Fields
Abstract
In this chapter, we demonstrate how some ideas originating in the analysis on groups can be applied in related settings without the group structure. In particular, in Chapter 7 we showed a number of Hardy and Rellich inequalities with weights expressed in terms of the so-called \(\mathcal{L}\)-gauge. There, the \(\mathcal{L}\)-gauge is a homogeneous quasi-norm on a stratified group which is obtained from the fundamental solution to the sub-Laplacian. At the same time, in Chapter 11 we used the fundamental solutions of the sub-Laplacian for the advancement of the potential theory on stratified groups, and in Section 7.3 fundamental solutions for the p-sub-Laplacian and their properties were used on polarizable Carnot groups for the derivation of further Hardy estimates in that setting.
Michael Ruzhansky, Durvudkhan Suragan
Backmatter
Metadaten
Titel
Hardy Inequalities on Homogeneous Groups
verfasst von
Prof. Michael Ruzhansky
Dr. Durvudkhan Suragan
Copyright-Jahr
2019
Electronic ISBN
978-3-030-02895-4
Print ISBN
978-3-030-02894-7
DOI
https://doi.org/10.1007/978-3-030-02895-4

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