The core-cusp problem is the discrepancy between the rotation curve of observed satellite galaxies and the dark matter density presumed to form satellite galaxies that occur in cosmological simulations, specifically simulations based on cold dark matter (CDM), such as those based upon the Lambda-CDM model. The cosmological simulations produce satellite galaxies forming around points of high dark matter density within dark matter halos, whereas the observed rotation curves of such galaxies are more varied, and generally suggesting less concentrated volumes of dark matter. For this issue, the terms cusp (mathematical term, for a more pointed concentration) and core (for lower, more smoothed concentration) have been adopted. The term caustic structure (borrowing caustic from optics) is used to describe a dark matter distribution with cusps. The problem has been a motivation for adjustments and/or alternatives to CDM, including warm dark matter (WDM) and fuzzy dark matter (FDM).