See this article https://www.sciencealert.com/new-study-brings-receipts-to-demonstrate-dark-matter-may-be-older-than-the-big-bang https://www.sciencealert.com/n

See this article https://www.sciencealert.com/new-study-brings-receipts-to-demonstrate-dark-matter-may-be-older-than-the-big-bang https://www.sciencealert.com/new-study-brings-receipts-to-de... which is an excellent overview of Tenkanen's paper the subject of this thread. It also puts the competing ideas about cosmic inflation into perspective.