  In this short note we give an explicit presentation of the algebra A_n
generated by the curvature 2-forms of the standard Hermitiam line bundles over
SL_n/B as the quotient of the polynomial ring. The difference between A_n and
H^*(SL_n/B) reflects the fact that SL_n/B is not a symmetric space. Possible
applications of A_n lie in the field of arithmetic intersection theory on flag
varieties.
