content_image/320536.jpg content_image/320537.jpg content_image/320538.jpg content_image/320543.jpg
However, the last column of ∇ $^{2}$G is 

<img src='content_image/320536.jpg'>

The combination of (83) and (84) yields (85). 

Therefore, 

<img src='content_image/320537.jpg'>

<img src='content_image/320538.jpg'>

Because both ∂ $^{2}$G ∂µ 2 and det ∇ $^{2}$G are nonnegative, G is a convex function. 

<img src='content_image/320543.jpg'>

(9) is a convex optimization problem because both the objective function and the feasible set are convex. 

