Members of a U.S. Federal Reserve (Fed) advisory committee expressed concerns this month that the central bank’s low interest-rate policies could be creating an “unsustainable bubble” in stock and bond markets. The discussion among members of the banking advisory committee and officials at the Fed show that the advisory group believed that the central bank’s policies have provided support for a slow economic recovery. But some members worry that the policies may also lead to higher inflation or market instability. The record of the May 17 discussion was published Friday on the Fed’s website. Under new procedures, the Fed will make the advisory committee records public two weeks after each quarterly meeting.