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We introduce a new method for constructing complex-valued $r$-harmonic functions on Riemannian manifolds. We then apply this method for the important semisimple Lie groups $SO(n)$, $SU(n)$, $Sp(n)$, $SL_n(R)$, $Sp(R,n)$, $SU(p,q)$,…

Differential Geometry · Mathematics 2019-11-26 Sigmundur Gudmundsson , Marko Sobak

We apply the method of eigenfamilies to construct new explicit complex-valued p-harmonic functions on the non-compact classical Lie groups, equipped with their natural semi-Riemannian metrics. We then employ this same approach to…

Differential Geometry · Mathematics 2023-03-12 Elsa Ghandour , Sigmundur Gudmundsson

We construct explicit proper p-harmonic functions on rank-one Lie groups of Iwasawa type. This class of Lie groups includes many classical Riemannian manifolds such as the rank-one symmetric spaces of non-compact type, Damek-Ricci spaces,…

Differential Geometry · Mathematics 2021-04-07 Sigmundur Gudmundsson , Anna Siffert , Marko Sobak

In this work we construct explicit complex-valued p-harmonic functions on the compact Riemannian symmetric spaces SU(n)/SO(n), Sp(n)/U(n), SO(2n)/U(n), SU(2n)/Sp(n). We also describe how the same can be manufactured on their non-compact…

Differential Geometry · Mathematics 2022-01-27 Sigmundur Gudmundsson , Anna Siffert , Marko Sobak

We develope a new scheme for the construction of explicit complex-valued proper biharmonic functions on Riemannian Lie groups. We exploit this and manufacture many infinite series of uncountable families of new solutions on the special…

Differential Geometry · Mathematics 2019-08-13 Sigmundur Gudmundsson , Anna Siffert

We characterize $p-$harmonic functions in the Heisenberg group in terms of an asymptotic mean value property, where $1<p<\infty$, following the scheme described in Manfredi et al. (2009) for the Euclidean case. The new tool that allows us…

Analysis of PDEs · Mathematics 2012-10-11 Fausto Ferrari , Qing Liu , Juan J. Manfredi

In this paper we introduce a new method for manufacturing harmonic morphisms from semi-Riemannian manifolds. This is employed to yield a variety of new examples from the compact Lie groups SO(n), SU(n) and Sp(n) equipped with their standard…

Differential Geometry · Mathematics 2007-05-23 Sigmundur Gudmundsson , Anna Sakovich

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

We define harmonic maps between sub-Riemannian manifolds by generalizing known definitions for Riemannian manifolds. We establish conditions for when a horizontal map into a Lie group with a left-invariant metric structure is a harmonic…

Differential Geometry · Mathematics 2023-08-23 Erlend Grong , Irina Markina

In this work we use the method of eigenfamilies to construct explicit complex-valued proper $p$-harmonic functions on the compact real Grassmannians. We also find proper $p$-harmonic functions on the real flag manifolds which do not descend…

Differential Geometry · Mathematics 2023-07-27 Elsa Ghandour , Sigmundur Gudmundsson

We consider spaces for which there is a notion of harmonicity for complex valued functions defined on them. For instance, this is the case of Riemannian manifolds on one hand, and (metric) graphs on the other hand. We observe that it is…

Metric Geometry · Mathematics 2016-08-16 Sylvain Barré , Abdelghani Zeghib

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 contrast to an infinite family of explicit examples of two-dimensional $p$-harmonic functions obtained by G.Aronsson in the late 80s, there is very little known about the higher-dimensional case. In this paper, we show how to use…

Analysis of PDEs · Mathematics 2021-02-12 Vladimir G. Tkachev

We construct the first known complex valued harmonic morphisms from the non-compact Lie groups SL(n,R), SU*(2n) and Sp(n,R) equipped with their standard Riemannian metrics. We then introduce the notion of a bi-eigenfamily and employ this to…

Differential Geometry · Mathematics 2007-05-23 Sigmundur Gudmundsson , Anna Sakovich

The main aim of this work is to construct several new families of proper biharmonic functions defined on open subsets of the classical compact simple Lie groups $\SU n$, $\SO n$ and $\Sp n$. We work in a geometric setting which connects our…

Differential Geometry · Mathematics 2016-08-31 Sigmundur Gudmundsson , Stefano Montaldo , Andrea Ratto

Let $1<p\le4$ when $n=1$ and $1<p< 3+\frac{1}{n-1} $ when $n\ge2$. We obtain the second-order horizontal Sobolev $HW^{2,2}_{\rm loc} $-regularity of $p$-harmonic functions in the Heisenberg group $\mathbb H^n$. This improves the known range…

Analysis of PDEs · Mathematics 2021-12-16 Jiayin Liu , Fa Peng , Yuan Zhou

Let $\h_n$ be the $(2n+1)$-dimensional Heisenberg group. and let ${\cal L}_\alpha$ be the sublaplacian of the Lie algebra of $\h_n$ A new spherical harmonics with its orthogonal polynomial properties is presented for the group.

Representation Theory · Mathematics 2025-08-13 M. E. Egwe

We introduce a class of non-commutative, complex, infinite-dimensional Heisenberg like Lie groups based on an abstract Wiener space. The holomorphic functions which are also square integrable with respect to a heat kernel measure $\mu$ on…

Probability · Mathematics 2008-09-30 Bruce Driver , Maria Gordina

Harmonic functions of the three dimensional Lie groups defined on certain manifolds related to the Lie groups themselves and carrying all their unitary representations are explicitly constructed. The realisations of these Lie groups are…

Mathematical Physics · Physics 2017-01-30 R. Campoamor-Stursberg , M. Rausch de Traubenberg

A new procedure for the construction of higher-dimensional Lie-Hamilton systems is proposed. This method is based on techniques belonging to the representation theory of Lie algebras and their realization by vector fields. The notion of…

Mathematical Physics · Physics 2024-11-26 Rutwig Campoamor-Stursberg , Oscar Carballal , Francisco J. Herranz
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