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An alternative theory for spiral structure.
This model offers a new perspective on spiral structure, attributing it to the interaction between a galaxy and its ghost matter environment. Françoise Combe's theory is based on the interaction between two populations: galactic matter and a mass of cold, undetectable hydrogen of unspecified origin. It should be noted that a two-population interaction model was already proposed in 1986 in my comic book A Thousand Billion Suns, Belin Editions.
We have conducted tests through 2D simulations. See: J.P. Petit and F. Landsheat: Matter and ghost matter astrophysics. 6: Spiral structure. [On this site: Geometrical Physics A, 9, 1998.]
There is no need to duplicate images. If possible, we will integrate onto the site a very suggestive animation showing the birth of a barred galaxy. Two regimes are observed. First, a strong dynamical friction causes significant deceleration of the galaxy. The bar forms rapidly, as do the spiral arms. Then deceleration becomes negligible. The system persists through many rotations, sustained by tidal effects. See the sequence of figures in the cited article.
Of course, these results must be treated with caution, as they are only 2D simulations. Our computational resources do not allow 3D simulations. Should a team wish to take over, we would be happy to provide all necessary technical details.
In classical simulations, the problem lies in ensuring the survival of spiral arms. In any case, the phenomenon corresponds to energy dissipation. The galaxy's components—stars—acquire significant velocities, leading to the disappearance of the spiral structure, which would then have to be re-established by a new influx of cold gas, for example.
In our model, the ghost matter environment appears to act as a "potential barrier," preventing objects from escaping. Thus, the galaxy retains its spiral arms for many rotations. However, this requires confirmation in 3D.
As mentioned above, we now have two new collaborators working on these simulation issues, and we are hopeful about their results (the sequence showing the formation of spiral arms in a galaxy dates back to 1994). The computing power of modern hardware, now accessible to ordinary individuals, allows us to "play in the big league" using just a personal computer. We can even manage enough "point masses" with such systems to soon represent galaxies as they truly are—comprising two very different populations in various aspects:
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The "Population I," or halo population, made up of old stars (and globular clusters), whose trajectories deviate significantly from the galactic equatorial plane.
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The "Population II," or disk population, dynamically grouping young stars and variable amounts of gas. This second group of masses is located very close to the galactic equatorial plane. It is within this population that spiral structure forms as a "density wave." This is a highly nonlinear phenomenon, which can even be likened to a "shock wave."
On the other hand, spiral structure affects Population I relatively little, despite the fact that it accounts for 90% of the galaxy's mass. It will be extremely interesting to finally get closer to astrophysical reality by representing galaxies not as a single population of point masses, but as two distinct populations.
The Radiative Phase.
Here, we return to the cosmological aspects of the model. As mentioned earlier, the linear initial solution—where R and R* near t = 0 grow proportionally to time—presents problems. Such an expansion would be far too slow to ensure the freezing of primordial nucleosynthesis. We were therefore led to connect this to earlier work from 1988–1989, available on the site:
J.P. Petit, Mod. Phys. Lett. A3 (1988) 1527
J.P. Petit, Mod. Phys. Lett. A3 (1988) 1733
J.P. Petit, Mod. Phys. Lett. A4 (1989) 2201
and:
J.P. Petit: Twin Universe Cosmology: Astronomy and Space Science
226: 273–307, 1995 and [See on the site: Geometrical Physics A, 2.]
The idea is then to assume that physical constants depend on energy density. In previous work, we showed that joint variations of physical constants could be considered, leaving all physical equations invariant (field equations, Schrödinger, Maxwell, etc.). We suggest that such a model could apply to the radiative phase, when energy-matter is primarily in the form of radiation.
As we go back in time, energy-matter density increases. When
r
r >>
r
m (when radiation energy density greatly exceeds matter density), we arrive at the following laws:
G being the gravitational constant, m the mass, h Planck's constant, c the speed of light, and e the electric charge. We take these quantities equal in both sheets (without justifying this choice).
Before describing this model in greater detail, let us provide its justification. As noted earlier, the remarkable homogeneity of the early universe, reflected in the 2.7 K cosmic microwave background, is difficult to explain within the standard framework. A new model—cosmic inflation—had to be added to the old Big Bang theory. For French speakers, this term is poorly translated. It comes from the English verb "to inflate," meaning "to expand." Thus, we are led—despite heavy assumptions—to suppose that the universe underwent a fantastic expansion in its earliest moments. This justifies its homogeneity. However, it should be noted that this is the only observational justification for Linde's model and the inflation theory. The cost remains relatively high.
Here, we consider that physical constants may depend on matter energy density beyond a certain threshold. This is no worse than the assumptions underlying inflation theory. But the benefit is double:
- We explain the homogeneity of the early universe
- We redefine the time variable.
For homogeneity, the explanation is straightforward. In the standard model with constant c, everything depends on comparing the horizon ct to the average distance between particles.
In this new view, referencing [On this site: Geometrical Physics A, 3, 1998, figure 17] and [Geometrical Physics A, 6, 1998, figure 10], while keeping the chronological variable t:
Cosmic homogeneity is thus ensured at all epochs.
This difference arises because the speed of light c increases as we go back in time.
See Figure 5 of reference [On this site: Geometrical Physics A, 6, 1998].
A quick remark:
For many years, we were the "eccentrics who amused themselves by varying the constants of physics..."