Evolution of the semi-major axis of the planet in an isothermal disk (model 1). In two simulations, the planet is started in a circular orbit at a distance of a₀ = 1.75 AU from the center of mass of the central binary. In the simulation shown in red, the planet is included in the disk from the very beginning of the simulation and it evolves as the disk evolves starting from its initial density profile. In the simulation shown in blue, the disk is first relaxed to the equilibrium and then the planet is embedded in it. In the simulation shown in green, the planet is started at a₀ = 1.0 AU in a relaxed disk. The inset shows the results near the end of the simulation for the first model. The dashed black line in the inset corresponds to the mean value of the planet’s semi-major axis at a_p = 0.436 AU.