Kronheimer–Mrowka basic class

In mathematics, the Kronheimer–Mrowka basic classes are elements of the second cohomology $H^2(X;\mathbb{Z})$ of a simply connected, smooth 4-manifold $X$ of simple type that determine its Donaldson polynomials. They were introduced by Peter B. Kronheimer and Tomasz S. Mrowka (1994, 1995).