# How does inflation justify the nonexistence of magnetic monopoles?

It is said that inflation justifies that magnetic monopoles don't exist. Can anyone explain how inflation theory explains the non existence of magnetic monopoles?

• PLease provide a reference for "It is said." – Carl Witthoft Dec 7 '17 at 16:28
• @ carl Witthoft . It was mentioned in wikipedia en.wikipedia.org/wiki/Inflation_%28cosmology%29 . Dr brian greene also mentioned in one of his lecture in world science festival, i'm sorry iam unable to find link for that. – Gauti Dec 8 '17 at 2:23

To get to your question now, I think it is an incorrect statement to say that inflation theory explains the non-existence of magnetic monopoles. What inflation theory does potentially explain, is the extremely low density of magnetic monopoles in the universe. The idea here is that magnetic monopoles, for some unknown reason, are extremely unlikely to form, even in the intensely energetic and hot crucible of the Big Bang. Some estimates say that for 1 magnetic monopole that formed, $10^{29}$ "normal" particles formed, making magnetic monopoles extremely sparse and rare.
Where inflation theory comes in is that it says the universe expanded exponentially fast. If the monopoles were already sparse before this extreme expansion, the expansion would have only served to cause the magnetic monopole density in the universe be practically zero. It is quite possible that, post-inflation, the magnetic monopole density in the universe is so low that only one exists within the observable universe. Good luck finding that single particle out of the $10^{80}$ particle haystack.