(Before It's News)
Bee wrote about Bullet Cluster. Usually Bullet Cluster is seen to favor dark matter and disfavor MOND theory introducing a modification of Newtonian gravity. Bee saw it differently.
Cold dark matter model (ΛCDM) and MOND are two competing mainstream models explaining the constant velocity spectrum of stars in galaxies.
- ΛCDM assumes that dark matter forms a spherical halo around galaxy and that its density profile is such that it gives the observed velocity spectrum of distant stars. The problem of the model is that dark matter distribution can have many shapes and it is not easy to understand why approximately constant velocity spectrum is obtained. Also the attempts to find dark matter particles identified as some exoticons have failed one after another. The recent finding that the velocity spectrum of distant stars around galaxies correlates strongly with the density of baryonic matter also challenges this model: it is difficult to believe that the halo would have so universal baryonic mass density.
- MOND does not assume dark matter but makes an ad hoc modification of gravitational force for small accelerations. The problem of MOND is that it is indeed an ad hoc modification and it is not easy to see how to make it consistent with general relativity: it is difficult to do cosmology using MOND. For small accelerations (small space-time curvatures) one would expect Newtonian theory to be an excellent approximation.
Consider now how Bullet Cluster relates to these two options. Bullet cluster is a pair of galaxy clusters which has emerged from collision (see the figure). There exists data at optical wavelenghts about stars. Stars experience only a small gravitational slowing down and are expected to go through the collision region rather fast. Data from X-ray measurements give information about the intergalactic gas associated with clusters. This gas interacts electromagnetically and is slowed down much more and remains in the collision region for a longer time. The red regions in the figure correspond to the gas. Gravitational lensing in turn gives information about space-time curvature and these two regions are farthest away from the collision center. These regions are blue and would naturally correspond to dark matter in ΛCDM model. Both models have severe problems.
- In cold dark matter model the event would require too high relative velocity for colliding clusters – about c/100. The probability for this kind of collision in cold dark matter model is predicted to be very low – about 6.4×10-6. Something seems to be wrong with ΛCDM model.
- In MOND the relative collision velocities are argued to be much more frequent. Bee however forgot to mention that in MOND the lensing is expected to be associated with X-ray region (hot gas in the center of figure) rather than with the blue regions disjoint from it. This observation is a very severe blow against MOND model.
The logical conclusion is that there indeed seems to be dark matter there but it is something different from the cold dark matter. What it could be? What could be the interpretation in TGD?
- Now galaxies are associated with cosmic string or more general string like objects like pearls with necklace: that this is the case is known for decades but for some mysterious reason to me has not been used as guideline in dark matter models. Maybe it is very difficult to see things from bigger perspective than galaxies.
The flux tubes carry Kähler magnetic energy, dark energy, and dark matter in TGD sense having heff=n×h. The galactic matter experiences transversal 1/ρ gravitational force predicting constant velocity spectrum for distant stars when baryonic matter is neglected. Note that one avoids a model for the profile of the halo altogether. The motion of the galaxy along the flux tube is free apart from the forces caused by galaxy. The presence of baryonic matter implies that the velocity increases slowly with distance up to some critical radius. By recent findings correlating observed velocity spectrum with density of baryonic matter one can deduce the density of baryonic matter (see this). A possible interpretation is as remants of cosmic string like object produced in its decay to ordinary matter completely analogous to the decay of the vacuum energy of inflaton field to matter in inflation theory.
- By fractality also galaxy clusters are expected to form similar linear structures. There are two options for interpreting the Bullet Cluster.
- The two colliding clusters could belong to the same string like object and move in opposite directions along it. In this case gravitational lensing would be most naturally associated with the flux tube and there would be single linear blue region instead of the two blue spots of the figure.
- The clusters could also belong to different flux tubes, which pass by each other and induce the collision of clusters and the gas associated with them. If the flux tubes are more or less parallel and orthogonal to the plane of the figure, the gravitational lensing would be from the two string like objects and two disjoint blue spots would appear in the figure. This option conforms with the figure.
It is difficult to say anything about the needed collision velocities. The collision velocity would correspond to the relative velocity of flux tubes. I am not able to say anything about the needed collision velocity or what collision velocities for flux tubes are probable.
For a summary of earlier postings see Latest progress in TGD.
Articles and other material related to TGD.