On The Structure Of Ext Groups Of Strongly Stable Ideals

We consider special classes of strongly stable ideals such as squarefree lexicographic ideals generated in one degree and principal strongly stable ideals. We prove a structure theorem for the Ext groups of such ideals. By means of earlier results on lexicographic ideals we also prove an upper bound theorem for the sheaf cohomology of some families of coherent sheaves on P-K(n).