Is the Hubble tension a hint of AdS around recombination?

Gen Ye, Yun-Song Piao

Published 2020-01-08Version 1

Anti-de Sitter (AdS) vacua, being theoretically important, might have unexpected impact on the observable universe. We find that in early dark energy (EDE) scenarios the existence of AdS vacua around recombination can effectively lift the CMB-inferred $H_0$ value. As an example, we study a phenomenological EDE model with an AdS phase starting at the redshift $z\sim2000$ and ending shortly after recombination (hereafter the universe will settle down in a $\Lambda>0$ phase till now), and obtain a best-fit $H_0=72.74$ km/s/Mpc without degrading the CMB fit compared with the standard $\Lambda$CDM model.