# notation for probability distribution (double absolute)

I am trying to understand this term in an equation, but I am somehow confused. Can someone clear it for me ?

$KL(q_2(z_2|x_2)||p_{\eta}(z))$

• Could you show us where you found this expression? – Bill Wallis Aug 22 '18 at 9:25
• $\mathcal{L}_{CC_2}(E_2, G_2, E_1, G_1) =\lambda_3 KL(q_2(z_2|x_2)||p_{\eta}(z)) + \lambda_3 KL (q_1(z_1|x_{2}^{2\rightarrow 1}||p_{\eta}(z)) - \lambda_4\mathbb{E}_{z_1\sim q_1(z_1|x_{2}^{2\rightarrow 1})}[\log p_{G_2}(x_2|z_1)]$ It is from a paper: arxiv.org/pdf/1703.00848.pdf – Mostafa Hussein Aug 22 '18 at 9:29
• I understand each variable, but I am confused in getting all variables related to each other inside the term itself – Mostafa Hussein Aug 22 '18 at 9:30

Kullback-Leibler divergence between the distribution $q_2$ of $z_2$ given $x_2$, and the distribution $p_\eta$ of $z$