Although it's invisible, dark matter accounts for at least 80 percent of the matter in the universe. No one knows what it is, but most scientists would bet on weakly interacting massive particles, or WIMPS.
They're not called WIMPs for nothing. ;-) To read more, click here.
I have given a plausible qualitative explanation.
I only assume
1) GR is correct
2) Lorentz invariance is correct.
3) Quantum field theory is correct.
those imply
virtual fermion-antifermion pairs have a Tuv source density that causes an attractive gravity field (dark matter)
virtual bosons have a Tuv source density that causes a repulsive gravity field (dark energy)
Exotic physics not needed. - Jack Sarfatti on 5-24-2012