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Colour Current

  The other model system that will be referred to arises from considering models of electrical conductivity within a dense plasma. In this case, we have two species of ion, positive and negative, interacting with a background field. The equations of motion for this system will be

where is the mass of each ion, its charge and the applied electric field. Note that in this equation, the momenta are chosen so that ve species is carrying of the current, where is the mass of the negative and positive ion respectively. In the particular case of , which we shall discuss henceforth, each species carries half the current. In a real electrical system, the forces must be sums of Coulomb terms (), which is effectively of infinite range, so there will be significant error involved in modelling it with the small systems available with computer simulations. There is a technique for resumming the electrical forces to take into account the screening effect [Allen and Tildesley [1987]] , but since at this stage we are interested in the feasibility of such calculations, rather realistic values, we take a simpler approach of using a short range force, such as the Lennard-Jones force.   We call this colour conductivity to   distinguish it from electrical conductivity, because we can consider that each molecule has a colour label which interacts with the colour field, but that the Hamiltonian is colour blind. A number of authors have studied this system [Evans and Morriss [1985], Evans et al. [1983], Erpenbeck [1987]] .



Russell Standish
Thu May 18 11:43:52 EST 1995