Is the Hubble Constant Scale-Dependent?

Resumo

An exact determination of the Hubble constant remains one of key problems in cosmology for almost a century. However, its modern values derived by various methods still disagree from each other by almost 10%, larger values being obtained by measurements at relatively small distances (e.g., by Cepheid stars as standard candles), while smaller values are characteristic of the methods associated with huge spatial scales (e.g., from the analysis of cosmic microwave background fluctuations). A reasonable way to resolve this puzzle is to assume that the Hubble constant is inherently scale-dependent. This idea seems to be particularly attractive in the light of the latest observational results on the early-type galaxies, where dark matter halos are almost absent. Therefore, an average contribution of the irregularly distributed dark matter to the rate of the cosmological expansion should be substantially different at various spatial scales. As follows from rough estimates, the corresponding variation of the Hubble constant can be about 10% and even more, which well explains the spread in its values obtained by different methods.