  In this master's thesis we study the production of axion dark matter through
the so-called misalignment mechanism by considering that during that time, the
universe was dominated by a new kind of fluid, different than radiation. We
perform a very detailed analysis of the oscillation temperature and the relic
density today, both analytically and numerically. Our findings show that on the
one hand, the oscillation temperature is strongly influenced by the
non-standard cosmology, affecting the relic density, and on the other hand, the
energy density of the axion gets diluted, because the new fluid eventually
decays, injecting entropy into the thermal bath. We find the predicted
parameter space of axion dark matter for different non-standard cosmologies and
we show its impact on the coupling of axions to two photons.
