A new contribution to the crisis of cosmology

Sabine Hossenfelder has a Youtube video (see this) about the latest anomaly in cosmology (see this). This anomaly is very problematic from the point of view of the ΛCDM scenario of dark energy and possibly also from the point of view of general relativity. The MOND scenario is however consistent with the findings.

The ΛCDM scenario involves 6 parameters. Among them is Hubble constant. Depending on the measurement method one obtains two values for it: this creates Hubble tension. The two kinds of measurements correspond to short and very long scales and this might relate to the problem.

There is also so called sigma8 tension with significance larger than 4 sigmas, which is something very serious. ΛCDM predicts that the Universe should become clumpier as it evolves. This implies that the gravitational potential wells should become narrower with time. In short scales the clumpying rate is not as high as predicted.

Also the new results from a dark energy survey based on gravitational lensing suggest that the gravitational valleys are shallower than they should be at large values of cosmic time.

1. What is measured is so-called Weyl potential Ψ_W=(Ψ+Φ)/2 defined in terms of the space-time metric in cosmic scales having the expression

   ds²= a²(τ)(1+2Ψ)dτ² -(1+2Φ)dx²₃) .

   Here τ and x₃ denote Minkowski coordinates. For Psi=Φ=0 one has conformally flat metric. From the value of Ψ_W one can deduce the clumpiness. The measurements are about 3 widely differing values of cosmic time τ. The value of the Weyl parameter Ψ_W characterizing the clumping differs from the prediction of the ΛCDM scenarioand is consistent with the increasing shallowness of the gravitational potentials of the mass distributions.

2. The significance of the finding is estimated to be 2-2.8 sigma, which is potentially significant. Since the same method is used for different cosmic times, it is not possible to claim that the discrepancy is due to the different methods.

MOND has no problems with the findings. What about TGD?

1. The TGD view of galactic dark matter as dark energy assignable to cosmic strings, which are 3-D extremely thin 3-surfaces with a huge density of magnetic and volume energy (see this). String tension parametrizes the density of this energy and creates a 1/ρ gravitational potential which predicts flat velocity spectrum for distant stars rotating around the galaxy. No dark matter halo nor dark matter particles are needed.
2. The 1/ρ gravitational potential created by cosmic strings makes the gravitational wells shallower than the sole 1/r² potential due to visible galactic matter. Also the halo creates 1/r² potential in long enough scales but the prediction is that the dark matter halo becomes more clumpy so that the gravitational wells should become sharper.

   Cosmic strings are closed so that there is some scale above which this effect is not seen anymore since the entire closed cosmic strings become the natural objects. Therefore this effect should not be seen in long enough scales.

   It is important to notice that the shallowing would be due to the shortening of the observation scale rather than due to the time evolution. The same interpretation applies to the Hubble constant. In the TGD framework, the finite size of space-time sheets indeed brings in a hierarchy of scales, which is not present in General Relativity.

3. How does this relate to MOND? The basic objection against MOND is that it is in conflict with mathematical intuition: for small accelerations Newtonian gravitation should work excellently. In TGD, the critical acceleration of MOND is replaced with a critical distance from the galactic nucleus at which the 1/ρ potential due to the cosmic string wins the 1/r² potential. Under a suitable assumption (see this), this translates to a critical acceleration of MOND so that the predictions are very similar. Note that the cosmic strings also cause a lensing effect used in the survey and this gives an upper bound for their string tension.

For a summary of earlier postings see Latest progress in TGD.

For the lists of articles (most of them published in journals founded by Huping Hu) and books about TGD see this.