On the Problem of Plateau / Subharmonic Functions PDF

A convex function f may be called sublinear in the following sense; if a linear function l is ::=: j at the boundary points of an interval, then l:> j in the interior of that interval also.

If we replace the terms interval and linear junction by the terms domain and harmonic function, we obtain a statement which expresses the characteristic property of subharmonic functions of two or more variables.

This ge- neralization, formulated and developed by F.

RIEsz, immediately at- tracted the attention of many mathematicians, both on account of its intrinsic interest and on account of the wide range of its applications.

If f (z) is an analytic function of the complex variable z = x + i y. then If (z) I is subharmonic. The potential of a negative mass-distribu- tion is subharmonic.

In differential geometry, surfaces of negative curvature and minimal surfaces can be characterized in terms of sub- harmonic functions.

The idea of a subharmonic function leads to significant applications and interpretations in the fields just referred to, and* conversely, every one of these fields is an apparently in- exhaustible source of new theorems on subharmonic functions, either by analogy or by direct implication.