# Understanding notation - strange use of the del operator

I'm currently reading a paper with the following notation with the del operator which i have never encountered before:

Does $\nabla _m$ just mean $\frac{\delta}{\delta \mathbf m}$ ? Furthermore, I have never seen $\nabla _m \nabla^T _m$ am I to interpret this as a matrix of partial derivatives?

• What are $m$ and $V$? Does $V$ depend on $m$? And what is the awkward notation $x^{\i}$? – Mark Viola May 2 '15 at 3:13
• m and v are the mean and variance of a multivariate gaussian, $m^{\i}$ is the mean of a separate gaussian – jshe857 May 2 '15 at 4:49