A scalar field model of this often has a field that forces the field of this toward the desired energy density at the present time in a slow rolling fashion, regardless of initial conditions. Trackers
A scalar field model of this often has a field that forces the field of this toward the desired energy density at the present time in a slow rolling fashion, regardless of initial conditions. Trackers that can be used in that model have pressure equal to the kinetic energy density minus the potential energy density. Because it causes gravitational potential to vary, this causes anisotropy in the CMB in the late-time integrated Sachs-Wolfe effect. It has negative pressure, and quintessence is one model of this, but a more common model involves a constant signified Lambda whose observed value differs from its theoretical value by (*) 120 orders of magnitude. That theory involving the cosmological constant postulates that vacuum fluctuations create this as there is a cost to having space. For 10 points, name this mysterious substance that causes the expansion of the universe and contains 70% of the universe's energy.
A scalar field model of this often has a field that forces the field of this toward the desired energy density at the present time in a slow rolling fashion, regardless of initial conditions.
dark energy [do not accept "dark matter"]