The Possibility of a Multi-fold Time-Varying Hubble Constant

- Stephane H Maes

## Abstract

The multi-fold theory provides microscopic interpretations to the universe accelerated expansion, inflation mechanisms and dark energy. From the beginning, the multi-fold dark matter main mechanisms have been identified as being stronger in the presence of matter, or energy increasing spacetime curvature. One could therefore naively expect that these mechanisms will also be globally time-dependent, when it comes to the early epochs of the universe. Indeed, during the early cosmological eras, including pre-CMB, different matter densities and curvatures reigned. Each would lead to a different global average cosmological constant. Such a reasoning would predict a Hubble constant that is larger for early time than late time observations. As discussed in multiple papers and articles, proposing a time-varying dark energy density can obviously be a simple way to address the Hubble constant tension: early time estimates would correspond to such a different value, and no Hubble constant tension would exist. However, in our naïve initial analysis above, obtaining larger pre-CMB values could a priori go in the wrong direction when it comes to observations: one would expect a larger Hubble constant at early times, unless if it is rather an additional contribution to the CMB derived Hubble constant. Considering the multi-fold dark energy mechanisms, in all the early stages of the universe, i.e., pre-CMB, aka pre-recombination, which led to the CMB, plasma, dominated by electromagnetic and possibly other interactions, occupied the whole concretized spacetime. This way, multi-fold dark energy effects were partially countered by more dominant interactions, and the resulting accelerations of expansion were reduced. It can explain why current early time estimates for the Hubble constant would differ from late time results, and lead to a smaller Hubble constant value at early time. However, it may not fit that well the overall standard cosmological model à la ΛCMD. However, note that recent papers show that a short term increase of the dark energy (5% for redshift z > 5000), can resolve the tension, by pushing up the CMB inferred Hubble constant, i.e. early time estimates, and better match overall the ΛCDM. So maybe our naïve reasoning was not that bad. Combining the two considerations above, our paper shows that multi-fold dark energy mechanisms intrinsically, and microscopically, justify such a behavior that can resolve the Hubble tension. It is another hint in favor of the multi-fold mechanisms, to add to several others. There is also a range where a multi-fold universe appear fractal, which may result into scaling of the cosmological constant, and reducing its value, during this period; again a move in the right direction. The result extends to the real universe, if it is multi-fold, as hinted by past results. ____ 1 shmaes.