 Embedding Condition 3: The infinitesimal  displacement \(\Sigma(M_{p}) \rightarrow \Sigma(M_{p'})\) will carry an  infinitesimal vector at the center of  \(\Sigma(M_{p})\), which is in one-to-one  correspondence with a vector at \(p \in M\), to the  center of \(\Sigma(M_{p'})\). 