The project intends to investigate galaxy formation models in the context of non-standard cosmological scenarios of dark energy (DE). These have been mainly investigated in the context of the standard cosmological model with cosmological constant Λ. Yet, the processes that lead to the formation of the most massive galaxies in the universe, especially at late time, may be sensitive to the dynamics of dark energy. The work will primarily focus on study of halo merger trees using the Excursion Set Theory framework, which provides a stochastic model description of dark matter halo assembly, a key ingredient of semi-analytic models of galaxy formation. The work is preparatory to a PhD project dedicated to the realisation of hydrodynamical simulations of galaxy formation in non-standard DE scenarios.