Dark Fluid? An extension of the current LambdaCDM model of the universe offers the first accurate prediction of the dark matter halo, the force holding rotating galaxies together. Professor James Farnes (Oxford University) has developed a mathematical model that explains the 95% of the universe not covered by the LambdaCDM model. This new theory shows that the universe is essentially a small proportion of "positive mass matter surfing on a sea of negative masses."

Press Article:
https://www.sciencedaily.com/releases/2018/12/181205093716.htm

Popular science article by James Farnes describing his work:
http://theconversation.com/bizarre-dark-fluid-with-negative-mass-could-dominate-the-universe-what-my-research-suggests-107922