The discussion revolves around the value of the Hubble parameter during periods of deceleration in the universe's expansion. Participants explore theoretical implications, mathematical relationships, and historical context related to the Hubble parameter, including its connection to the universe's dynamics and the transition from deceleration to acceleration.
Participants express differing views on the existence and implications of deceleration and acceleration in the universe's expansion. There is no consensus on the precise value of the Hubble parameter during deceleration, and multiple competing views remain regarding its historical values and significance.
The discussion highlights limitations in the precision of measurements related to the Hubble parameter and the dependence on various cosmological models and parameters. The calculations and estimates provided are subject to uncertainties and assumptions inherent in cosmological modeling.
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!