Usually denoted by the lowercase letter a, for ten points, identify this time-dependent quantity, a parameter which multiplies length scales to account for the effects of cosmic inflation.
Using the geodesic equation, it is possible to show that the magnitude of the three-momentum depends inversely on this quantity. Because the early universe is radiation-dominated, its energy density scales as the fourth power of this quantity, while number densities of particles after decoupling are proportional to its third power. The Hubble rate is defined by the time-derivative of this quantity over itself, and it appears as a prefactor to the spatial component in the Friedmann-Robertson-Walker metric. The exponential increase in this quantity forms the basic idea of the theory of inflation and one plus the redshift is defined as the ratio between this value in the past and this value today. Usually denoted by the lowercase letter a, for ten points, identify this time-dependent quantity, a parameter which multiplies length scales to account for the effects of cosmic inflation.
Using the geodesic equation, it is possible to show that the magnitude of the three-momentum depends inversely on this quantity.
{scale factor} [accept a or a of {t} before mention]