Extrapolation in Grand Function Spaces

In this chapter, we derive extrapolation results, generally speaking, in grand Banach function spaces (GBFS briefly) \(E^{p), \varphi (\cdot )}\) . In particular, we are interested in the extrapolation in weighted grand Lebesgue and Lorentz spaces under the Muckenhoupt conditions on weights. The same problem is studied in general Banach function spaces (BFS briefly) and GBFSs. These results imply, in particular, the boundedness of operators of harmonic analysis in the mentioned spaces.