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We give a completely explicit formula for all harmonic maps of finite uniton number from a Riemann surface to the unitary group U(n) in any dimension, and so all harmonic maps from the 2-sphere, in terms of freely chosen meromorphic…

Differential Geometry · Mathematics 2009-09-01 Maria João Ferreira , Bruno A. Simões , John C. Wood

We use filtrations of the Grassmannian model to produce explicit algebraic formulae for all harmonic maps of finite uniton number from a Riemann surface, and so all harmonic maps from the 2-sphere, to the unitary group for a general class…

Differential Geometry · Mathematics 2010-08-12 Martin Svensson , John C. Wood

We classify all harmonic maps with finite uniton number from a Riemann surface into an arbitrary compact simple Lie group $G$, whether $G$ has trivial centre or not, in terms of certain pieces of the Bruhat decomposition of the group…

Differential Geometry · Mathematics 2014-05-16 Nuno Correia , Rui Pacheco

We extend many known results for harmonic maps from the 2-sphere into a Grassmannian to harmonic maps of finite uniton number from an arbitrary Riemann surface. Our method relies on a new theory of nilpotent cycles arising from the diagrams…

Differential Geometry · Mathematics 2022-09-13 Rui Pacheco , John C. Wood

We investigate in detail the connection between harmonic maps from Riemann surfaces into the unitary group $\U(n)$ and their Grassmannian models: these are families of shift-invariant subspaces of $L^2(S^1,\C^n)$. With the help of…

Functional Analysis · Mathematics 2019-10-16 Alexandru Aleman , Rui Pacheco , John C. Wood

We establish explicit formulae for canonical factorizations of extended solutions corresponding to harmonic maps of finite uniton number into the exceptional Lie group $G_2$ in terms of the Grassmannian model for the group of based…

Differential Geometry · Mathematics 2010-07-27 N. Correia , R. Pacheco

In this paper, we develop a loop group description of harmonic maps $\mathcal{F}: M \rightarrow G/K$ ``of finite uniton type", from a Riemann surface $M$ into inner symmetric spaces of compact or non-compact type. This develops work of…

Differential Geometry · Mathematics 2023-02-10 Josef F. Dorfmeister , Peng Wang

In [5], together with J. C. Wood, the authors gave a completely explicit formula for all harmonic maps from $2$-spheres to the unitary group $U(n)$ in terms of freely chosen meromorphic functions on $S^2$. The simplest harmonic maps are the…

Differential Geometry · Mathematics 2015-02-11 Maria João Ferreira , Bruno Ascenso Simões

In this paper, we discuss the associated family of harmonic maps $\mathcal{F}: M \rightarrow G/K$ from a Riemann surface $M$ into inner symmetric spaces of compact or non-compact type which are either algebraic or totally symmetric. These…

Differential Geometry · Mathematics 2024-08-23 Josef F. Dorfmeister , Peng Wang

In this paper, we develop a loop group description of harmonic maps $\mathcal{F}: M \rightarrow G/K$ of finite uniton number, from a Riemann surface $M,$ compact or non-compact, into inner symmetric spaces of compact or non-compact type. As…

Differential Geometry · Mathematics 2024-08-26 Josef F. Dorfmeister , Peng Wang

In this paper we describe how the operation of adding a uniton arises via the DPW method of obtaining harmonic maps into compact Riemannian symmetric spaces out of certain holomorphic one forms. We exploit this point of view to investigate…

Differential Geometry · Mathematics 2007-12-11 N. Correia , R. Pacheco

In this paper we give a unified framework for the construction of complex valued harmonic morphisms from the real, complex and quaternionic Grassmannians and their non-compact duals. This gives a positive answer to the corresponding open…

Differential Geometry · Mathematics 2007-05-23 Sigmundur Gudmundsson , Martin Svensson

We consider harmonic maps on simply connected Riemann surfaces into the group $\mathrm{U}(n)$ of unitary matrices of order $n$. It is known that a harmonic map with an associated algebraic extended solution can be deformed into a new…

Functional Analysis · Mathematics 2017-02-22 Alexandru Aleman , María J. Martín , Anna-Maria Persson , Martin Svensson

We classify all harmonic maps of finite uniton number from a Riemann surface into SU(n) in terms of certain pieces of the Bruhat decomposition of the subgroup of algebraic loops in SU(n). We give a description of the "Frenet frame data" for…

Differential Geometry · Mathematics 2013-04-17 N. Correia , R. Pacheco

This paper aims to provide a description of totally isotropic Willmore two-spheres and their adjoint transforms. We first recall the isotropic harmonic maps which are introduced by H\'elein, Xia-Shen and Ma for the study of Willmore…

Differential Geometry · Mathematics 2016-04-12 Peng Wang

In this paper, we construct polynomial growth harmonic maps from once-punctured Riemann surfaces of any finite genus to any even-sided, regular, ideal polygon in the hyperbolic plane. We also establish their uniqueness within a class of…

Differential Geometry · Mathematics 2016-05-26 Andy C. Huang

Biharmonic and conformal-biharmonic maps are two fourth-order generalizations of the well-studied notion of harmonic maps in Riemannian geometry. In this article we consider maps into the Euclidean sphere and investigate a geometric…

Differential Geometry · Mathematics 2026-03-09 Volker Branding

We construct explicit complex-valued $p$-harmonic functions and harmonic morphisms on the classical compact symmetric complex and quaternionic Grassmannians. The ingredients for our construction method are joint eigenfunctions of the…

Differential Geometry · Mathematics 2023-08-22 Elsa Ghandour , Sigmundur Gudmundsson

A harmonic map from a Riemannian manifold into a Grassmannian manifold is characterized by a vector bundle, a space of sections of this bundle and a Laplace operator. We apply our main theorem, itself a generalization of a Theorem of…

Differential Geometry · Mathematics 2014-08-08 Yasuyuki Nagatomo

In this paper, the theory of functions of one complex variable is explored to study linearly full unramified holomorphic two-spheres with constant curvature in $G(2,n)$ satisfying that the generated harmonic sequence degenerates at position…

Differential Geometry · Mathematics 2020-03-06 Jie Fei , Ling He
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