Grand Unified Theories of particle physics predict the production of magnetic monopoles – massive, stable particles carrying a net magnetic charge – during symmetry-breaking transitions in the early universe. According to standard thermodynamic calculations, such monopoles should have been copiously produced in the first fractions of a second. Yet no magnetic monopoles have ever been observed. Their (apparent) complete absence from the observable universe is a mystery: if they exist and were produced as expected, they should now dominate the mass density and (it is presumed) be detectable in cosmic ray experiments. Inflation offers a solution by “diluting” the monopole density through exponential expansion, but this just leads to even more problems.
In Two-phase Cosmology, inflation is no longer part of the model. So if the monopoles weren't diluted by inflation, where are they? In the Two-phase Cosmology, the monopoles are Dark Matter.