These systems have Hamiltonians that do not explicitly depend on time, and Helmholtz decomposition shows that one negative term can represent this type of field.
In 1975, Vujanovic extended Noether's theorem to this type of system, and the presence of a term proportional to the quantity "x-squared minus one" results in the Van der Pol oscillator not being this type of system.  These systems have Hamiltonians that do not explicitly depend on time, and Helmholtz decomposition shows that one negative term can represent this type of field. Fields of this type have no curl, and can be described as the gradient of a scalar potential.  For 10 points, identify this adjective which refers to systems in which the amount of work done is independent of the path, and describes fields such as the gravitational and electric fields in which no energy is lost.
In 1975, Vujanovic extended Noether's theorem to this type of system, and the presence of a term proportional to the quantity "x-squared minus one" results in the Van der Pol oscillator not being this type of system.  
conservative