Ext1-quivers for the Witt algebra W(1,1)

Let g be the finite-dimensional Witt algebra W(1,1) over an algebraically closed field of characteristic p>3. It is well known that all simple W(1,1)-modules are finite-dimensional. Each simple module admits a character χ∈g∗. Given χ∈g∗ one can form the (finite-dimensional) reduced enveloping algebra u(g,χ). The simple modules for u(g,χ) are precisely those simple W(1,1)-modules admitting the character χ. In this paper the authors compute Ext1 between pairs of simple modules for u(g,χ).