We study the cosmological evolution for a universe in the presence of a continuous tower of massive scalar fields which can drive the current phase of accelerated expansion of the universe and , in addition , can contribute as a dark matter component .
The tower consists of a continuous set of massive scalar fields with a gaussian mass distribution .
We show that , in a certain region of the parameter space , the heavy modes of the tower ( those with masses much larger than the Hubble expansion rate ) dominate at early times and make the tower behave like the usual single scalar field whose coherent oscillations around the minimum of the potential give a matter-like contribution .
On the other hand , at late times , the light modes ( those with masses much smaller than the Hubble expansion rate ) overcome the energy density of the tower and they behave like a perfect fluid with equation of state ranging from 0 to -1 , depending on the spectral index of the initial spectrum .
This is a distinctive feature of the tower with respect to the case of quintessence fields , since a massive scalar field can only give acceleration with equation of state close to -1 .
Such unique property is the result of a synergy effect between the different mass modes .
Interestingly , we find that , for some choices of the spectral index , the tower tracks the matter component at high redshifts ( or it can even play the role of the dark matter ) and eventually becomes the dominant component of the universe and give rise to an accelerated expansion .