An accelerating closed universe

The dark matter which makes up 99% or more of the Universe by mass is now believed to contain four separate ingredients: dark baryons, massive neutrinos, "exotic" cold dark-matter particles and vacuum energy, also known as the cosmological constant (Lambda). Of these, only baryons fit within the current standard model of particle physics. The fourth (vacuum) component has come into new prominence in the past few years, largely at the expense of the third (exotic dark matter). We argue here that vacuum energy may be dominant enough to remove the need for exotic dark matter and close the accelerating Universe.