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(abridged) We present simulations of halo formation and evolution in scalarfield dark matter (SFDM) cosmologies in the Thomas-Fermi regime, aka``SFDM-TF", where a strong repulsive 2-particle self-interaction (SI) isincluded, being a valuable alternative to CDM, with the potential to resolveits ``cusp-core" problem. In general, SFDM behaves like a quantum fluid.Previous literature has presented two fluid approximations for SFDM-TF, as wellas simulations of halo formation. These results confirmed earlier expectationsand are generally in mutual agreement, but discrepancies were also reported.Therefore, we perform dedicated 3D cosmological simulations for the SFDM-TFmodel, applying both fluid approximations, as well as for CDM. Our results arevery well in accordance with previous works and extend upon them, in that wecan explain the reported discrepancies as a result of different simulationsetups. We find some interesting details: The evolution of both SFDM-TF and CDMhalos follows a 2-stage process. In the early stage, the density profile in thecenter becomes close to a $(n=1.5)$-polytropic core, dominated by an"effective" velocity-dispersion pressure $P_{\sigma}$ which is common to bothdark matter models. Consecutively, for CDM halos, the core transitions into acentral cusp. In SFDM-TF halos, the additional pressure $P_\text{SI}$ due to SIdetermines the second stage of the evolution, where the central region followsclosely a $(n=1)$-polytropic core, embedded in a nearly isothermal envelope,i.e. the outskirts are similar to CDM. We also encounter a new effect, namely alate-time expansion of both polytropic core plus envelope, because the size ofthe almost isothermal halo envelope is affected by the expansion of thebackground universe. So, an initial primordial core of $\sim 100$ pc can evolveinto a larger core of $\gtrsim 1$ kpc, even without feedback from baryons.

Halo formation and evolution in scalar field dark matter and cold dark matter: New insights from the fluid approach