Examples of groups

Projective semilinear group

Let 𝑉 be a vector space over 𝕂. The projective semilinear group PΓL(𝑉) is the semidirect product group

PΓL(𝑉)=Aut(𝕂)PGL(𝑉)

where PGL(𝑉) is the projective general linear group acted on by 𝜎 Aut(𝕂) coördinatewise, so 𝜎[𝐴]𝜎1[𝐱] =[𝜎(𝐴)][𝐱]. By the Fundamental theorem of projective geometry this forms the collineätion group of the projectivization P(𝑉).


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