Dear all, I am concerned with a question which I posted on MSE, but didn't received much attention. So I thought maybe one of you might be able to help me out. Please follow the link math.stackexchange.com/questions/1554739/…
There is also a comment to the question by myself, which you should take under consideration.
@user66288: This is going to be true in the specific case you mention (K=Q,H=P intersect Q, P a parabolic) because your map G/H->G/K factors as G/H->G/K x G/P->G/K. The first map is an embedding (and hence projective) and the second map is a product with G/P->pt (and hence projective because G/P is projective.)
