Suppose \(\Omega\) is a domain . A function \(u\in C^2(\Omega)\) is called subharmonic if \(\Delta u \ge 0\), where \(\Delta\) is the Laplace operator .
If \(\Delta u < 0\) we call \(u\) superharmonic.
Remarks
Suppose \(\Omega\) is a domain . A function \(u\in C^2(\Omega)\) is called subharmonic if \(\Delta u \ge 0\), where \(\Delta\) is the Laplace operator .
If \(\Delta u < 0\) we call \(u\) superharmonic.