On the Chemical Potential of Dark Energy

It is widely assumed that the observed Universe is accelerating due to the existence of a new uid component called dark energy. In this article, the thermodynamics consequences of a nonzero chemical potential on the dark energy component is discussed with special emphasis to the phantom uid case. It is found that if the dark energy uid is endowed with a negative chemical potential, the phantom eld hypothesis becomes thermodynamically consistent with no need of negative temperatures as recently assumed in the literature.