Pfaffian constraint
In dynamics, a Pfaffian constraint is a way to describe a dynamical system in the form: ∑ s = 1 n A r s d u s + A r d t = 0 ; r = 1 , … , L {\displaystyle \sum _{s=1}^{n}A_{rs}du_{s}+A_{r}dt=0;\;r=1,\ldots ,L} where L {\displaystyle L} is the number of equations in a system of constraints, and A r s , A r {\displaystyle A_{rs},A_{r}} are functions of t , u 1 , … , u n {\displaystyle t,u_{1},\dots ,u_{n}} only. In other words, it is a 1-form on R 1 + n {\displaystyle \mathbb {R} ^{1+n}} .