Closed Universe? Local H0 Measurements & Relativistic Corrections

[Chronos]

In this paper; http://arxiv.org/abs/1405.7860, What is the distance to the CMB? How relativistic corrections remove the tension with local H0 measurements, it is suggested cosmological distance may be miscalculated due to failure to take into account systematic accumulation of lensing effects. The authors go on to suggest this may explain the tension between local and cosmological measurements of the Hubble constant and could mean the universe may, in fact, be closed.

 

[Drakkith]

Interesting. Thanks, Chronos.

 

[Tanelorn]

Thanks Chronos. I had wondered myself what percentage of the CMB photons make it to Earth without interacting with matter along the way and how much this distorts the CMB temperature and black body shape?

 

[Chronos]

I view this as consistent with Rees & Sciama [http://adsabs.harvard.edu/full/1968ApJ...153L...1R], who noted that large density perturbations interposed between the CMB surface and an observer can have an effect if the fluctuations change while photons traverse them. They experience more blue-shift infalling than when climbing out because expansion makes the wells shallower, giving rise to a net blue-shift of CMB photons. A similar effect can accumulate as photons pass through interposing gravitational lenses.

 

[Lino]

... expansion makes the wells shallower ...

Can you elabort on how expansion makes a well shallower? (Wider I get, and steeper on the way in than on the way out, I understand.)

Thanks in advance.