Hi,

If we define the convolution of two functions $\displaystyle f,g:\mathbb{R}^n \longrightarrow \mathbb{R}$ to be $\displaystyle f* g(x) = \int_{\mathbb{R}^n} f(x-y)g(y)dy$ then this operation is supposed to commute, i.e. $\displaystyle f* g = g* f$. When you change variables though, surely you get a minus sign???

Any help would be greatly appreciated.