Skip to Main Content


AMS eBook CollectionsOne of the world's most respected mathematical collections, available in digital format for your library or institution


Q-valued functions revisited

About this Title

Camillo De Lellis, Institut für Mathematik, Universität Zürich, Winterthurerstrasse 190 CH-8057 Zürich and Emanuele Nunzio Spadaro

Publication: Memoirs of the American Mathematical Society
Publication Year: 2011; Volume 211, Number 991
ISBNs: 978-0-8218-4914-9 (print); 978-1-4704-0608-0 (online)
DOI: https://doi.org/10.1090/S0065-9266-10-00607-1
Published electronically: July 27, 2010
Keywords: $Q$-valued functions; Dirichlet energy; existence and regularity; metric spaces; harmonic maps
MSC: Primary 49Q20, 35J55, 54E40, 53A10

PDF View full volume as PDF

View other years and numbers:

Table of Contents

Chapters

  • Introduction
  • 1. The elementary theory of $Q$-valued functions
  • 2. Almgren’s extrinsic theory
  • 3. Regularity theory
  • 4. Intrinsic theory
  • 5. The improved estimate of the singular set in $2$ dimensions

Abstract

In this note we revisit Almgren’s theory of $Q$-valued functions, that are functions taking values in the space $\mathcal {A}_Q(\mathbb {R}^{n})$ of unordered $Q$-tuples of points in $\mathbb {R}^{n}$. In particular:

  • we give shorter versions of Almgren’s proofs of the existence of $\mathrm {Dir}$-minimizing $Q$-valued functions, of their Hölder regularity and of the dimension estimate of their singular set;
  • we propose an alternative, intrinsic approach to these results, not relying on Almgren’s biLipschitz embedding $\xi : \mathcal {A}_Q(\mathbb {R}^{n})\to \mathbb {R}^{N(Q,n)}$;
  • we improve upon the estimate of the singular set of planar $\mathrm {D}$-minimizing functions by showing that it consists of isolated points.
  • References [Enhancements On Off] (What's this?)

    References