Physical interpretations of the Fermi gamma-ray excess

The so-called gamma-ray excess observed by Fermi-LAT has received different physical interpretations: i) Dark Matter annihilation in the Galactic center ii) a population of millisecond pulsars in the Galactic center, and iii) suppressed emission from molecular clouds. The excess may also be partially caused by detector effects originating from the limited angular resolution of the instrument. In this talk we first discuss the impact of detector effects on the signal shape and then discuss physical interpretation of the signal.