  Cosmic voids, the underdense regions in the Universe, are impacted by dark
energy and massive neutrinos. In this work, relying on the DEMNUni suite of
cosmological simulations, we explore the void size function in cosmologies with
both dynamical dark energy and massive neutrinos. We investigate the impact of
different choices of dark matter tracers on the void size function and study
its sensitivity to the joint effect of modifying the dark energy equation of
state and the sum of neutrino masses. We show that dark energy and massive
neutrinos produce separable effects on the void size function. This statistic
therefore allows us to distinguish among a wide range of combinations of dark
energy equations of state and total neutrino masses, and its exploitation in
forthcoming large galaxy surveys will be extremely useful in breaking
degeneracies among these cosmological parameters.
