Semi-entwining structures and their applications

Semi-entwining structures are proposed as concepts simpler than entwining structures, yet they are shown to have interesting applications in constructing intertwining operators and braided algebras, lifting functors, finding solutions for Yang-Baxter systems, etc. While for entwining structures one can associate corings, for semi-entwining structures one can associate comodule algebra structures where the algebra involved is a bialgebra satisfying certain properties.