if one has a group G acting on a mathematical object (or se…

if one has a group G acting on a mathematical object (or set of objects) X, then one may ask which points x are unchanged, "invariant" under the group action, or under an element g of the group.
https://twetch.app/t/a63c84a3d94c34cf0f96cd9da0203ab2decb64dee93392fdbc1c883494245ddd