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  • Research Article
  • Open Access

On Nonhomogeneous -Harmonic Equations and 1-Harmonic Equations

Journal of Inequalities and Applications20102010:346308

  • Received: 31 December 2009
  • Accepted: 7 February 2010
  • Published:


We prove a characterization of a nonhomogeneous A-harmonic equation and describe its generalization. We also point out its connection with 1-Harmonic equation.


  • Continuous Function
  • Weak Solution
  • Open Problem
  • Usual Sense
  • Harmonic Extension

1. Introduction

Both A-harmonic equations and -harmonic geometry are rich subjects [15]. Many results on both topics have been derived, respectively, but there are very few papers relating both subjects. In this paper, we will connect these two subjects by extending several results from 1-Harmonic functions to A-Harmonic functions.

We consider the following setting: a function is said to be A-harmonic if it is a weak solution of A-harmonic equation


where is the length of the gradient of , and for a function without a critical point, is said to be the 1-tension field of .

Let be an open subset of . Consider the following second-order divergence-type elliptic equation:


where x satisfies

(i) ,

(ii) ,

where are two fixed constants, and is called a weight if and a.e. Also, in general where is a weight.

In this paper, we characterize subsolutions of (1.1) and indicate its generalization to (1.2). We first recall some results in homogeneous A-harmonic equations in the following section, followed by the main results in Section 3. Some open problems are discussed in the last section.

2. Homogeneous -Harmonic Equations


A function , is called a very weak solution of (1.2) if

for all with compact support.

It was shown in [4] that very weak solutions of (1.2) in fact weak solutions of (1.2) in the usual sense.

Definition 2.2.

an -harmonic tensor in of satisfies the -harmonic equation (2.1) in .

Consider the space of differential -forms being an A-harmonic tensor in a domain , and Assume that , and for some . Then the following local weighted Poincare inequality for A-harmonic tensors was proved in [3]. There exists a constant independent of such that


for all balls with , where the measure is defined by , and is the ball with the same center as and with .

3. Characterizations of Nonhomogeneous -Harmonic Equations

In what follows, we prove an A-harmonic analog of 1-harmonic equations.

Lemma 3.1.

Let M be a complete noncompact Riemannian. For any and any pair of positive numbers with , there exist a rotational symmetric Lipschitz continuous function and a constant (independent of ) with the following properties:

(i) on B( ; s) and off B ( ; s),

(ii) , a.e. on M.


See Andreotti and Vesentini [6], Yau [7], and Karp [8].

Theorem 3.2.

Let be a domain in containing a ball of radius , centered at , and let be a continuous function with , and
Let be a weak solution of

then the infimum c satisfies , where k only depends on , and .


Let be as in Lemma 3.1, and . Choose to be a test function. Then by Cauchy-Schwarz inequality, we have

Hence, .

Where only depends on and .

Corollary 3.3.

Let be a weak subsolution of -harmonic equation (1.1) with constant 1-tension field , that is, in the distribution sense. Then is an A-harmonic function.


In a similar fashion, the above results can be extended to the nonhomogeneous equation by using Sobolev Imbedding Theorem.

4. Further Discussions

It would be interesting to find similar results of Section 2 for nonhomogeneous -harmonic equations. It would also be interesting to seek analogs of 1-harmonic applications in calibration geometry. The extension of 1-harmonic functions to -harmonic functions on hyperbolic spaces and their associated spaces could be explored.

To conclude this paper, we state another -harmonic extension of 1-harmonic result [5], that is an immediate consequence of Corollary 3.3.


Let , and for every x in . The following statements are equivalent.

(i) is a weak subsolution of (1.1) with constant 1-tension field.

(ii) is a weak solution of (1.1) on .

(iii) is a A-harmonic function on .



The author wishes to express sincere gratitude to Professor S. Walter Wei for many helpful suggestions and encouragements without which this would have not been written.

Authors’ Affiliations

Department of Mathematics, Central Michigan University, Mount Pleasant, MI 48859, USA


  1. Agarwal RP, Ding S: Advances in differential forms and the A -harmonic equation. Mathematical and Computer Modelling 2003, 37(12–13):1393–1426. 10.1016/S0895-7177(03)90049-5MathSciNetView ArticleMATHGoogle Scholar
  2. Ding S: Integral estimates for the Laplace-Beltrami and Green's operators applied to differential forms on manifolds. Zeitschrift für Analysis und ihre Anwendungen 2003, 22(4):939–957.View ArticleMATHGoogle Scholar
  3. Ding S, Liu B: Generalized Poincaré inequalities for solutions to the A -harmonic equation in certain domains. Journal of Mathematical Analysis and Applications 2000, 252(2):538–548. 10.1006/jmaa.2000.6951MathSciNetView ArticleGoogle Scholar
  4. Gao H-Y, Zhang Y, Chu Y-M: Regularity for very weak solutions of -harmonic equation with weight. Kyungpook Mathematical Journal 2009, 49(2):195–202.MathSciNetView ArticleMATHGoogle Scholar
  5. Wei SW: On 1-harmonic functions. Symmetry, Integrability and Geometry: Methods and Applications 2007, 3: 127–136.MathSciNetMATHGoogle Scholar
  6. Andreotti A, Vesentini E: Carleman estimates for the Laplace-Beltrami equation on complex manifolds. Institut des Hautes Études Scientifiques. Publications Mathématiques 1965, (25):81–130.Google Scholar
  7. Yau ST: Some function-theoretic properties of complete Riemannian manifold and their applications to geometry. Indiana University Mathematics Journal 1976, 25(7):659–670. 10.1512/iumj.1976.25.25051MathSciNetView ArticleMATHGoogle Scholar
  8. Karp L: Subharmonic functions on real and complex manifolds. Mathematische Zeitschrift 1982, 179(4):535–554. 10.1007/BF01215065MathSciNetView ArticleMATHGoogle Scholar


© En-Bing Lin 2010

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.