Nonisospectral negative Volterra flows and mixed Volterra flows: Lax pairs, infinitely many conservation laws and integrable time discretization

In this paper, by means of the discrete zero curvature representation, nonisospectral negative Volterra flows and mixed Volterra flows are proposed. By means of solving corresponding discrete spectral equations, we demonstrate the existence of infinitely many conservation laws for the two nonisospectral flows and obtain the formulae of the corresponding conserved densities and associated fluxes. Integrable time discretizations for several isospectral equations of the two flows are also presented.