multinomial distributions over words) {ψ c,t,n } that generate words in turn t and the topics {ψ c,t−1,n } that generate words in turn t − 1 come from the same distribution.
all topics used in a segment s are drawn from a single distribution, For notational convenience, S c denotes the number of segments in conversation c, and s t denotes the segment index of turn t. We emphasize that all segment-related notations are derived from the posterior over the topic shifts l and not part of the model itself.