Universality of Period Doubling in Coupled Maps

We study the critical behavior of period doubling in two coupled one-dimensional maps with a single maximum of order $z$. In particurlar, the effect of the maximum-order $z$ on the critical behavior associated with coupling is investigated by a renormalization method. There exist three fixed maps of the period-doubling renormalization operator. For a fixed map associated with the critical behavior at the zero-coupling critical point, relevant eigenvalues associated with coupling perturbations vary depending on the order $z$, whereas they are independent of $z$ for the other two fixed maps. The renormalization results for the zero-coupling case are also confirmed by a direct numerical method.