The Stacks project

Lemma 78.9.2. In the situation of Definition 78.9.1.

  1. The algebraic space $X$ is a pseudo $G$-torsor if and only if for every scheme $T$ over $B$ the set $X(T)$ is either empty or the action of the group $G(T)$ on $X(T)$ is simply transitive.

  2. A pseudo $G$-torsor $X$ is trivial if and only if the morphism $X \to B$ has a section.

Proof. Omitted. $\square$

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