A curvature form for pseudoconnections
  We obtain the curvature form $F^\nabla=P\circ d^\nabla\circ\nabla-d^\nabla\circ P\circ\nabla+d^\nabla\circ\nabla\circ P$ for a vector bundle pseudoconnection $\nabla$, where $d^\nabla$ is the exterior derivative associated to $\nabla$. We use $F^\nabla$ to obtain the curvature of $\nabla$. We also prove that $F^\nabla=0$ is a necessary (but not sufficient) condition for $d^\nabla$ to be a chain complex. Instead we prove that $F^\nabla=0$ and $d^\nabla\circ d^\nabla\circ\nabla=0$ are necessary and sufficient conditions for $d^\nabla$ to be a {\em chain $2$-complex}, i.e., $d^\nabla\circ d^\nabla\circ d^\nabla=0$. 
C.A. Morales, M. Vilches
math.DG