content_image/304178.jpg content_image/304184.jpg content_image/304185.jpg
ative. This part can be shown by using a Cauchy-Schwarz inequality. 

<img src='content_image/304178.jpg'>

∴ ∂ $^{2}$G ∂µ 2 is always nonnegative. 

Second, we show that det ∇ $^{2}$G ≥ 0 . 

From (77), we calculate ∂ $^{2}$G ∂ω$_{k}$∂µ where k ∈ { 1 , 2 , ..., N } . 

<img src='content_image/304184.jpg'>

Similarly, 

<img src='content_image/304185.jpg'>

