Morita–Takeuchi Contexts Acting on Graded Coalgebras

In this paper, we introduce the concept of graded Morita–Takeuchi contexts and prove that every graded Morita–Takeuchi context induces a Morita–Takeuchi context between the 1-components of the corresponding coalgebras. We also establish an action of Morita–Takeuchi contexts on graded coalgebras, which is important for the development of the action of Picard groups on graded coalgebras.Partially supported by the NNSF of China and the YNSF of Shandong Province (No. Q98A05113).1991 Mathematics Subject Classification: 16W30, 16W50, 16D90