A Minimum Halo Mass from the Bounce: The Low-Mass End of the Halo Mass Function

If the initial fluctuation spectrum is cut off at a bounce wavenumber, then below a corresponding mass there are essentially no seeds from which dark matter halos can grow. A cutoff at 10 per megaparsec implies a minimum halo mass of 5.16e+09 solar masses; at 50 per megaparsec the minimum falls to 4.13e+07 solar masses; and at 5 per megaparsec it rises to 4.13e+10 solar masses, a value that would already struggle to accommodate the smallest observed dwarfs. The mass function therefore supplies an independent, late-time route to the same cutoff that the initial-variance calculation bounds from the early side, and the two routes agree on the scale at which the effect would become visible. Computed from stated assumptions, not measured.