The variety J orn of Jordan unitary algebra structures on k n , k an algebraically closed field with char k 6= 2 , is studied, as well as infinitesimal deformations of Jordan algebras. Also we establish the list of ...

We define representations of weighted posets and construct for them reflection functors. Using this technique we prove that a weighted poset is of finite representation type if and only if its Tits form is weakly positive; ...