We deterministically compute multinomial parameters β by exponentiating and normalizing: This normalization could introduce identifiability problems, as there are multiple settings for η that maximize P (w|η) (Blei and Lafferty, 2006a).
this difficulty is obviated by the priors: given µ and σ 2 , there is only a single η that maximizes P (w|η)P (η|µ, σ 2 ); similarly, only a single µ maximizes P (η|µ)P (µ|a, b 2 ).