Stronger Validity Criteria for Encoding Synchrony

We analyse two translations from the synchronous into the asynchronous $\pi$-calculus, both without choice, that are often quoted as standard examples of valid encodings, showing that the asynchronous $\pi$-calculus is just as expressive as the synchronous one. We examine which of the quality criteria for encodings from the literature support the validity of these translations. Moreover, we prove their validity according to much stronger criteria than considered previously in the literature.