Electronic Journal of Differential Equations, Vol. 2010(2010), No. 48, pp. 1-14. Title: Green function and Fourier transform for o-plus operators Author: Wanchak Satsanit (Maejo Univ., Chiang Mai, Thailand) Abstract: In this article, we study the o-plus operator defined by $$ \oplus^k =\Big(\Big(\sum^{p}_{i=1}\frac{\partial^2}{\partial x^2_i}\Big)^{4}-\Big(\sum^{p+q}_{j=p+1}\frac{\partial^2}{\partial x^2_j}\Big)^{4}\Big)^k , $$ where $x=(x_1,x_2,\dots,x_n)\in \mathbb{R}^n$, $p+q=n$, and $k$ is a nonnegative integer. Firstly, we studied the elementary solution for the $\oplus^k $ operator and then this solution is related to the solution of the wave and the Laplacian equations. Finally, we studied the Fourier transform of the elementary solution and also the Fourier transform of its convolution. Submitted January 8, 2010. Published April 06, 2010. Math Subject Classifications: 46F10, 46F12. Key Words: Fourier transform; diamond operator; tempered distribution.