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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

In this paper we give a positive answer to the open existence problem for complex-valued harmonic morphisms from the non-compact irreducible Riemannian symmetric spaces $SL_n(R)/SO(n)$, $SU^*(2n)/Sp(n)$ and their compact duals $SU(n)/SO(n)$…

Differential Geometry · Mathematics 2009-11-11 Sigmundur Gudmundsson , Martin Svensson

We construct new complex-valued harmonic morphisms from Euclidean spaces from functions which are holomorphic with respect to Hermitian structures. In particular, we give the first global examples of complex-valued harmonic morphisms from…

dg-ga · Mathematics 2008-02-03 P. Baird , J. C. Wood

In this work we construct a variety of new complex-valued proper biharmonic maps and (2,1)-harmonic morphisms on Riemannian manifolds with non-trivial geometry. These are solutions to a non-linear system of partial differential equations…

Differential Geometry · Mathematics 2023-03-14 Elsa Ghandour , Sigmundur Gudmundsson

We classify the harmonic morphisms with one-dimensional fibres (1) from real-analytic conformally-flat Riemannian manifolds of dimension at least four, and (2) between conformally-flat Riemannian manifolds of dimensions at least three.

Differential Geometry · Mathematics 2007-05-23 Radu Pantilie

We introduce the natural notion of (p,q)-harmonic morphisms between Riemannian manifolds. This unifies several theories that have been studied during the last decades. We then study the special case when the maps involved are…

Differential Geometry · Mathematics 2021-04-05 Elsa Ghandour , Sigmundur Gudmundsson

We consider four dimensional Lie groups with left-invariant Riemannian metrics. For such groups we classify left-invariant conformal foliations with minimal leaves of codimension two. These foliations produce local complex-valued harmonic…

Differential Geometry · Mathematics 2015-06-17 Sigmundur Gudmundsson , Martin Svensson

We present an explicit description of all harmonic maps of finite uniton number from a Riemann surface into a complex Grassmannian. Namely, starting from a constant map $Q$ and a collection of meromorphic functions and their derivatives, we…

Differential Geometry · Mathematics 2010-07-26 Maria Joao Ferreira , Bruno Ascenso Simoes

We construct large families of harmonic morphisms which are holomorphic with respect to Hermitian structures by finding heierarchies of Weierstrass-type representations. This enables us to find new examples of complex-valued harmonic…

dg-ga · Mathematics 2008-02-03 P. Baird , J. C. Wood

We use functions of a bicomplex variable to unify the existing constructions of harmonic morphisms from a 3-dimensional Euclidean or pseudo-Euclidean space to a Riemannian or Lorentzian surface. This is done by using the notion of…

Differential Geometry · Mathematics 2010-03-12 Paul Baird , John C. Wood

We introduce the complete lifts of maps between (real and complex) Euclidean spaces and study their properties concerning holomorphicity, harmonicity and horizontal weakly conformality. As applications, we are able to use this concept to…

dg-ga · Mathematics 2008-02-03 Ye-lin Ou

We present a new method for manufacturing complex-valued harmonic morphisms from a wide class of Riemannian Lie groups. This yields new solutions from an important family of homogeneous Hadamard manifolds. We also give a new method for…

Differential Geometry · Mathematics 2010-05-24 Sigmundur Gudmundsson , Jonas Nordström

In this paper we introduce two new methods for constructing harmonic morphisms from solvable Lie groups. The first method yields global solutions from any simply connected nilpotent Lie group and from any Riemannian symmetric space of…

Differential Geometry · Mathematics 2007-09-05 Sigmundur Gudmundsson , Martin Svensson

We construct harmonic Riemannian submersions that are retractions from symmetric spaces of noncompact type onto their rank-one totally geodesic subspaces. Among the consequences, we prove the existence of a non-constant, globally defined…

Differential Geometry · Mathematics 2025-06-17 F. E. Burstall

In this work we find a unifying scheme for the known explicit complex-valued eigenfunctions on the classical compact Riemannian symmetric spaces. For this we employ the well-known Cartan embedding for those spaces. This also leads to the…

Differential Geometry · Mathematics 2025-02-20 Sigmundur Gudmundsson , Adam Lindström

We construct 4-dimensional Riemannian Lie groups carrying left-invariant conformal foliations with minimal leaves of codimension 2. We show that these foliations are holomorphic with respect to an (integrable) Hermitian structure which is…

Differential Geometry · Mathematics 2014-05-22 Sigmundur Gudmundsson

The nonnegative Grassmannian is a cell complex with rich geometric, algebraic, and combinatorial structures. Its study involves interesting combinatorial objects, such as positroids and plabic graphs. Remarkably, the same combinatorial…

Combinatorics · Mathematics 2018-06-15 Alexander Postnikov

We introduce O-systems (Definition \ref{DO}) of orthogonal transformations of ${\Bbb R}^{m}$, and establish $1-1$ correspondences both between equivalence classes of Clifford systems and that of O-systems, and between O-systems and…

dg-ga · Mathematics 2008-02-03 Ye-lin Ou

In this paper we classify those three-dimensional Riemannian Lie groups which admit harmonic morphisms to surfaces.

Differential Geometry · Mathematics 2010-03-23 Sigmundur Gudmundsson , Martin Svensson

The present article studies holomorphic isometric embeddings of the complex two--plane Grassmannnian into quadrics. We discuss the moduli space of these embeddings up to gauge and image equivalence using a generalisation of do…

Differential Geometry · Mathematics 2021-10-26 Oscar Macia , Yasuyuki Nagatomo
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