Emerging spatial curvature can resolve the tension between high-redshift
  CMB and low-redshift distance ladder measurements of the Hubble constant
  The measurements of the Hubble constant reveal a tension between
high-redshift (CMB) and low-redshift (distance ladder) constraints. So far
neither observational systematics nor new physics has been successfully
implemented to explain this tension away. This paper present a new solution to
the Hubble constant problem. The solution is based on the Simsilun simulation
(relativistic simulation of the large scale structure of the Universe) with the
ray-tracing algorithm implemented. The initial conditions for the Simsilun
simulation were set up as perturbations around the $\Lambda$CDM model. However,
unlike in the Standard Cosmological Model (i.e. $\Lambda$CDM model +
perturbations), within the Simsilun simulation relativistic and nonlinear
evolution of cosmic structures leads to the phenomenon of emerging spatial
curvature, where the mean spatial curvature evolves from spatial flatness of
the early universe towards slightly curved present-day universe. Consqeuently,
the present-day expansion rate is slightly faster compared to the spatially
flat $\Lambda$CDM model. The results of the ray-tracing analysis show that the
universe which starts with initial conditions consistent with the Planck
constraints should have the Hubble constant $H_0 = 72.5 \pm 2.1$ km s$^{-1}$
Mpc$^{-1}$. When the Simsilun simulation was re-run with no inhomogeneities
imposed, the Hubble constant inferred within such a homogeneous simulation was
$H_0 = 68.1 \pm 2.0$ km s$^{-1}$ Mpc$^{-1}$. Thus, the inclusion of nonlinear
relativistic evolution that leads to the emergence of the spatial curvature can
explain why the low-redshift measurements favour higher values compared to
high-redshift constraints and alleviate the tension between the CMB and
distance ladder measurements of the Hubble constant.
