Mikheyev-Smirnov-Wolfenstein effect for linear electron density

When the electron density is a linear function of distance, it is known tha t the MSW equations for two neutrino species can be solved in terms of know n functions. It is shown here that more generally, for any number of neutri no species, these MSW equations can be solved exactly in terms of single in tegrals. While these integrals cannot be expressed in terms of known functi ons, some of their simple properties are obtained. Application to the solar neutrino problem is briefly discussed.