•E.g.,
neutrinos with rest mass on order of eV.
•Highly relativistic
when they decouple (around transition
from radiation to matter domination)
•Does NOT create
large perturbations in the background
radiation (good!).
•Accounts
for “cellular structure” seen.
•Predicts
the largest scale structures grow first
•Fails to predict
correlation functions on the right
scales and galaxies form very late (bad!).
–
•
•