Some textbooks describe accelerated expansion with an H value, as shown in the two figure above. It is said that the H value is accelerated because it is smaller in the past and larger in the present. On the contrary, during the deceleration expansion period, the value of H was greater in the past.
However, a proper explanation explains acceleration expansion with the acceleration of the scale factor. In fact, the Hubble constant decreases with time, and in the distant future, the Hubble constant becomes constant, that is, the exponential expansion era is reached.
Why do many textbooks insist on explaining acceleration expansion with H? I think it's a wrong way of explaining.!
