Text size About the author: Susan Thornton is a retired U.S. diplomat and former acting assistant secretary of state for East Asia and Pacific affairs. She is currently a senior fellow at the Paul Tsai China Center at Yale University Law School. Treasury Secretary Janet Yellen is traveling this week to China for crucial discussions between these two huge economies. She will have much to discuss, with markets in a state of unease and global growth stalled. But the most important aspect of the trip may simply be that it is happening at all, after months in which the two…