In mathematics, given the action σ:G×SX→X{\displaystyle \sigma :G\times _{S}X\to X} of a group scheme G on a scheme (or stack) X over a base scheme S, an equivariant sheaf F on X is a sheaf of OX{\displaystyle {\mathcal {O}}_{X}}-modules together with the isomorphism of OG×SX{\displaystyle {\mathcal {O}}_{G\times _{S}X}}-modules