The Hubble parameter, which describes the rate of expansion of the universe, was approximately 150 km/s/Mpc when the universe transitioned from deceleration to acceleration, based on calculations using WMAP parameters. This transition occurred around a redshift of 1.5, approximately 4.3 billion years ago. The discussion highlights that the Hubble parameter has varied significantly over time, with its value during the deceleration phase being roughly twice its current value. The relationship between the Hubble parameter and the universe's expansion dynamics is governed by the equation of state and energy density components.
PREREQUISITESAstronomers, cosmologists, and physics students interested in the dynamics of the universe's expansion and the historical values of the Hubble parameter.
Not easily. Basically you'd have to go back to evaluate the integrals numerically (they can't be solved by hand).zeebo17 said:During inflation the scale factor behaves as a \propto e^{Ht} and during a radiation dominated era it behaves as a \propto t^{1/2} and then during a matter dominated era behaves as a \propto t^{2/3}.
So then is it correct to say that during inflation: H= \dot{a}/a \propto constant
radiation dominated era: H= \dot{a}/a \propto 1/t
matter dominated era: H= \dot{a}/a \propto 1/t
from simply taking the derivative and dividing by a?
Does the Hubble parameter behave as 1/t during these eras? How would you find how it behaves during an era with mixed conditions, such as the present?
Thanks!