A new $({\gamma }_n,{\sigma }_k)-$ KP hierarchy and generalized dressing method

A new (\gamma_n,\sigma_k)-KP hierarchy with two new time series \gamma_n and \sigma_k, which consists of \gamma_n-flow, \sigma_k-flow and mixed \gamma_n and \sigma_k evolution equations of eigenfunctions, is proposed. Two reductions and constrained flows of (\gamma_n,\sigma_k)-KP hierarchy are studied. The dressing method is generalized to the (\gamma_n,\sigma_k)-KP hierarchy and some solutions are presented.