Here is part of the abstract of the article:
For four decades, the roughly flat rotation curve (RC) of the Milky Way (MW) stood as local evidence for an extended dark matter (DM) halo. Gaia DR3 has changed the picture: several analyses now find a velocity decline beyond R ≈ 15 kpc, and the most radical interpretation claims a nearly Keplerian fall-off (v ∝ R-1/2) that excludes a flat RC at 3σ and implies a total dynamical mass of only ≈ 2 × 1011Msun-three to five times below pre-Gaia estimates. Taken at face value, this would make the MW exceptional among comparable spirals and challenge both ΛCDM and MOND. It would also alter predictions for direct-detection experiments, although the local DM density is not fixed by virial mass alone.
The findings challenge not only the ΛCDM model and MOND but also the TGD view of the galaxies, galactic dark matter, and galaxy formation (this).
The TGD based model (see this) for the formation of galaxies and of also smaller structures relies on the notions of cosmic string and flux tube.
- Galactic dark matter is identified as the volume energy and Kähler magnetic energy assignable to long cosmic strings orthogonal to the galactic plane. Also cosmic strings parallel to the plane can be considered and collisions of nearly orthogonal cosmic strings could have given rise to spiral galaxies.
Galaxies would correspond to tangles along the cosmic strings. Thickening of the cosmic string would have liberated energy and produced ordinary matter somewhat like in the decay of the inflaton field in cosmic inflation. The cylindrical geometry of the model predicts flat velocity spectrum but also implies testable deviations from the halo model.
- The radius of the visible part of the Milky way is about R=100,000 ly. The critical distance at which the rotation curve ceases to be flat is 15 kpc, that is 48,923 light-years, roughly R/2. The average distance between galaxies is L= 1-few million ly and suggests that the average distance of galaxies along cosmic strings is roughly L.
- In the modification of Λ CDM, the dark mass halo should be concentrated near the centre. This implies that the dark matter of the galaxy is about 3/4 of the recent estimate and smaller than the cosmological average. For MOND the challenge is much more difficult to overcome. In TGD the galactic dark matter is along the long cosmic string so that the problem disappears.
The TGD based model for the formation of galaxies and of also smaller structures relies on the notions of cosmic string and flux tube.
- Galactic dark matter is identified as volume energy and K\"ahler magnetic energy assignable to long cosmic strings transversal (not necessarily orthogonal) to the galactic plane. Also cosmic strings parallel to the plane can be considered and collisions of transversal cosmic strings could have given rise to spiral galaxies \cite{btart/3pieces}.
Galaxies would correspond to tangles along the cosmic strings. Thickening of the cosmic string would have liberated energy and produced ordinary matter somewhat like in the decay of the inflaton field in cosmic inflation. The cylindrical geometry of the model predicts flat velocity spectrum but also implies testable deviations from the halo model.
- The radius of the visible part of the Milky way is about R=100,000 ly. The critical distance at which the rotation curve ceases to be flat is 15 kpc, that is 48,923 light-years, roughly R/2. The average distance between galaxies is L= 1-few million ly and suggests that the average distance of galaxies along cosmic strings is roughly L.
- In the modification of ΛCDM, the dark mass halo should be concentrated near the centre. This implies that the dark matter of the galaxy is about 3/4 of the recent estimate and smaller than the cosmological average. For MOND the challenge is much more difficult to overcome. In TGD the galactic dark matter is along the long cosmic string.
- The monopole flux tubes and cosmic strings as extremely thin flux tubes are necessarily closed. If the return flux is along a single parallel monopole flux tube, there would be a violation of the planar asymmetry in the rotation curve caused by the weakening of gravitational force at one side and strengthening at the other side. The effect would increase at large distances and cause an approximate Keplerization. The rotation velocity would have a strong dependence on the direction in the galactic plane.
- Could one think that the return flux is branched to less heavier flux tubes returning along a wall or could be also along thin cylindrical flux sheets? In this case one can however argue that the effect of a constant cylindrical mass distribution would however vanish in the entire interior so that this option fails.
- The most plausible option is that a lattice of parallel cosmic strings transversal to a plane defined by the galactic plane causes Keplerization. Monopole flux tubes bring in mind ferromagnets and antiferromagnets. The cancellation of the gravitational fields of neighboring cosmic strings would cause approximate Keplerization of the velocity curve.
What kind of lattice?
One can consider several kinds of 2-D lattices of cosmic strings.
- Triangular and hexagonal lattices having the same symmetries, rectangular lattices with or without center points, and oblique lattices, can be considered. The lattices spanned by a parallelogram appear as moduli spaces of toric conformal structures and of elliptic Riemannian surfaces \cite{btart/Weierstrass}.
- The square lattice would conform with the approximate 4-fold rotation planar symmetry assignable to the quadrupole harmonics (l=2). The quadrupole in the distribution of temperature fluctuations can be visualized as a collection of 4 charges at the vertices of parallelogram in the plane orthogonal to the Axis of Evil.
Octupole 8 has charges at the vertices of a cube projecting to 3+3=6 charges in the plane dissecting the diagonal of the cube giving rise to a hexagon. Axis of Evil is therefore in the direction of the diagonal of the cube which is in the plane of the solar system. The hexagonal symmetry also suggests the possibility of a hexagonal lattice of cosmic strings.
- The fluctuation patterns for the CMB temperature (quadrupole and octopole) on the sky and divide the sky to two hemispheres relative to us. The octupole variation reflects itself as a division of the ecliptic to 8 angular sectors such that hot and cool sectors alternate.
- Many-sheeted-ness with respect to CP2 (space-time surface as multi-sheeted graph over CP2) could mean this kind of lattice: different flux tubes would be sheets over CP2. This option could be consistent with the cosmic estimate for the density of the dark matter.
- 15 kpc= 48,923 ly gives an idea about the density of parallel cosmic strings orthogonal to the galactic plane. The distance of cosmic strings should be larger but not too much so. The radius for the visible part of the Milky Way radius is 100,000 ly and roughly twice this scale so that the distance between cosmic strings should be larger than the radius of the visible galaxy.
- One could image a lattice of parallel cosmic strings with lattice spacing of 100-200 ly. Cosmic strings would have galaxies as tangles along them with average separation of 1-few million ly. The distance between parallel cosmic strings would be roughly by factor 1/10 smaller if it corresponds to galactic radius. Cylindrical symmetry is however violated. The effect is largest at large enough distances and should reflect the symmetry of the planar lattice.
- Could the galaxies along cosmic strings form 3-dimensional lattice like structure, at least in an approximate sense? The typical distance between galaxies along the string would be about 1 million years and about 10 times larger than the distance between cosmic strings so that cubes would be stretched along the body diagonal to form a rhombohedron, which can have the same edge lengths as a cube.
Axis of Evil
Cosmic microwave background has a mysterious property, which is in conflict with the cosmological principle.
- The fluctuation patterns (dipole, quadrupole and octupole) characterized by moments are are aligned along the same direction, the Axis of Evil \cite{bcast/AxisofEvil}, which is defined as the normal vector for these planar fluctuation patterns and is directed along the ecliptica and points toward the constellations Leo and Virgo. Since CMB was created much before the solar system, this kind of correlation is impossible in the standard cosmology.
- Galactic plane and the plane of the solar system (ecliptic) are tilted and intersect at an angle about 60 degrees. If the Axis of Evil as direction of cosmic strings is transversal to the galactic plane and parallel to the ecliptic it has an angle of 60 degree with respect to the galactic plane.
- Is it possible to understand why this angle is 60 degrees? Cube has 8 face diagonals which do not intersect the main diagonal and have an angle of 60 degrees with it. The directions of diagonals of opposite faces are the same, which leaves 3 directions defining normals of 3 planes. One of these 3 face diagonals could be the direction of the normal of the galactic plane.
- Axis of Evil as direction of cosmic strings would be along the ecliptic and the projection to the ecliptic would consist of hot and cool lobes.
- Axis of Evil means that temperature and mass density fluctuations break translational symmetry along the direction of cosmic strings. If this direction were normal to the galactic plane, a large mass in the galactic plane could explain the asymmetry. Could the galaxies along the cosmic strings, having a typical distance of million light years, somehow give rise to the anomaly?
Could the distances of the nearest galaxies at opposite sides be different and cause a local anomaly? Or could the linear density of galaxies vary in the direction of the Axis of Evil causing global anomaly. Why so? Could one think that the formation of galaxies was a wave, a kind of phase transition, propagating in the direction of cosmic strings?
- In the TGD framework, the cosmic strings would have existed already before the formation of galaxies. The planes assignable to galaxies, in particular the Milky Way, and stellar system would be determined to a high degree by this primordial cylindrical symmetry.
- The plane of ecliptic as a preferred plane appears in cosmic scales, which suggests that it must have existed before the time when CMB was generated and reflects the presence of an effective 2-dimensionality of the Universe. If the density of galaxies varies along the cosmic strings, the CMB fluctuations would reflect this variation.
See the article About the recent TGD based view concerning cosmology and astrophysics or the chapter with the same title.