i think Hubble constant is not a constant because of relativistic speeds of galaxies. is it?
You're right that the thing we call the Hubble parameter, H, which relates recessional velocity to proper distance, is not constant. It changes with time, and so it can be expressed as a function H(t). However, your reason is wrong: it has nothing to do with "relativistic speed" of galaxies. It changes with time in a manner determined by the Friedmann equations, which describe the large-scale dynamics of the universe in terms of its matter and energy content.i think Hubble constant is not a constant because of relativistic speeds of galaxies. is it?