出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We establish the equation of motion of pseudoscalar particles coupled to an electro- magnetic field in a classical gravitational background through the use of conformal time and flat geometry. We show that the expansion of the universe can lead to larger mixing than in a station- ary universe. We also show that for a broad range of parameters, one can obtain resonant mixing, i.e. a region in which the mixing becomes maximum.
