The variational posteriors q φ (z x |x) and q φ (z y |y) follow Gaussian distributions parameterized by the outputs of feedforward networks, whose inputs are x and y.
the Kullback-Leibler (KL) divergence between q φ (z x |x) and the isotropic Gaussian prior So we only need to model µ x and the diagonal of Σ x to compute the KL divergence.