Group action

Category of G-spaces

The category of (left) 𝐺-spaces \leftindex{G}\Set for a given group 𝐺 consists of sets (left-)acted on by 𝐺 (called a (left-)𝐺-space) with 𝐺-(left-)equivariant maps as morphisms. group A (left-)equivariant map 𝑓 ∈𝐺{(}𝑋,π‘Œ) is a function 𝑓 :𝑋 β†’π‘Œ satisfying

𝑓(𝑔⋅π‘₯)=𝑔⋅𝑓(π‘₯)

for any π‘₯ βˆˆπ‘‹ and 𝑔 ∈𝐺. An isomorphism of 𝐺-spaces is sometimes called an equivalence of actions.


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