As my title already says: can the ELBO be negative?
$ELBO_\lambda = KL[q_\lambda(w)||P(w)] - \mathbb{E}_q[\log P(\mathcal{D|w})] $
Can I theoretically adjust my prior $P(w)$ such that $KL=0$ and also $\mathbb{E}_q>0$? If yes, why call it a lower bound on evidence? Since $P(\mathcal{D}) \geq 0$ per definition and a negative lower bound has no information.
