The absolute luminosity of SnIa may be calibrated using two distinct independent calibrators: 1. The sound horizon at recombination ($z\sim 1100$) used as a standard ruler to set the scale for the LCDM H(z) and thus the SnIa absolute magnitude and luminosity (inverse distance ladder approach) 2. The locally calibrated  standard candles like Cepheid stars which measure the distance to SnIa host galaxies at low redshifts ($z<0.01$, $D<40Mpc$) and thus calibrate the absolute luminosity $L$ and magnitude $M_B$ of SnIa (distance ladder approach). The two approaches lead to values of the SnIa absolute magnitude $M_B$ that are inconsistent at a level more than $4\sigma$. This inconsistency is known as a Hubble tension because the difference in the values of $M_B$ is easily translated in a difference in the values of the Hubble constant $H_0$ since $H_0$ and $M_B$ are degenerate. The two measurements of $M_B$ however are performed in different redshift ranges: The Cepheid measurement is performed for $z<0.01$ where Cepheids are detectable and the measurement using the sound horizon is performed for $z>0.01$ where the Hubble flow and the LCDM $H(z)$ are applicable. Thus, the two measurements can be made consistent if a fundamental physics transition changes the SnIa absolute luminosity ($M_B$) at a redshift $z\lesssim 0.01$. In this presentation I will summarize the independent observational evidence that indicates that such a transition may indeed have taken place focusing mainly on a new Cepheid data analysis but also on other astrophysical data. Theoretical speculation about the possible origin of such a transition will also be implemented.  

Relevant papers: 

https://arxiv.org/abs/2109.04406  Hubble tension or a transition of the Cepheid SnIa calibrator parameters? 

https://arxiv.org/abs/2105.05208  Challenges for \LambdaΛCDM: An update 

https://arxiv.org/abs/2104.14481  Hints for a gravitational constant transition in Tully-Fisher data 

https://arxiv.org/pdf/2102.06012.pdf  Rapid transition of Geff at zt< 0.01 as a possible solution of the Hubble and growth tensions 

https://arxiv.org/abs/2012.13932  A w？M phantom transition at zt<0.1 as a resolution of the Hubble tension