I have a question related to the following equations which are addressed in the section 3 of D3PM (Austin et al., 2021, NIPS, arXiv: 2107.03006v3: https://arxiv.org/pdf/2107.03006.pdf).
It's about transition matrix Q that is used in discrete diffusion models.
My question is, when I rewrote the left hand side of eq. (3), I got the eq. (4). How can I convert eq.(4) to eq. (3)?
