a201
The Twin Bang and the problem of the age of our universe.
The study of the joint evolutions of these twin universes corresponds to the two following papers:
- J.P. Petit & P. Midy : Astrophysics of ghost-matter - matter. 3 : The radiative era : The problem of the "origin" of the universe. The problem of the homogeneity of the primitive universe. Geometrical Physics A, 6, 1998.
- J.P. Petit & P. Midy : Astrophysics of ghost-matter - matter. 1. The geometrical framework. The matter era and the newtonian approximation. Geometrical Physics A, 4, 1998. ** **
...We can define length scales R and R*. We study the evolution with respect to the time t of our first universe, supposed to be ours (but possibly: t* = -t). In a word: we decide to describe the evolutions of the two universes with the same time-marker t.
...During the radiative era, we assume that R(t) varies like R*(t). We assume that the two universes are strongly coupled. Thus, when the radiative era ends in both universes, the matter-dominated era begins. Let us first examine this second period.
...If the two densities r and r* are assumed to be equal (in the matter-dominated era, the pressures p and p* are negligible, as in the classical Friedmann models), the tensors T and T* are equal. Then, the field equations reduce to:
(142)
S = S* = 0
whose common solution is (143)
R = R* = ct
and corresponds to a linear expansion in both universes. We show in the cited paper that this expansion is unstable. One of the two universes begins to expand faster than the other, which slows down. *See Geometrical Physics A, 4, 1998, section 2.
*(144)
...The two laws R(t) and R*(t) deviate from their initial common linear evolution. We assume R(t) corresponds to our own universe. In figure (145), the standard model, with a null cosmological constant.
(145)
...In 1994, the journal Nature raised a serious problem regarding the age of the universe, following measurements performed by the Hubble space telescope on distant galaxies, where the satellite had discovered cepheids.
...It turned out that the distances of these galaxies had been overestimated. The corresponding new value of the Hubble constant, increased, reduced the age of the universe to 8 to 9 billion years.
...Until 1994, the age of the oldest stars in our galaxy, located in globular clusters, was estimated to be about 15 to 20 billion years.
...After the measurements performed in 1993-1994 by the Hubble telescope, the universe became younger than its own stars!
...Four years later, the situation does not seem quite so critical, for two reasons.
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Following measurements by the Hipparcos satellite, the calibration of cepheids was modified.
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The theorists made great efforts to reduce the age of the oldest stars in globular clusters.
But this problem is not yet closed.
...The following figure shows how the Twin Bang model systematically increases the age of our universe, compared to the Standard Model (dotted line) for a given value of the Hubble constant Ho.
(146)
...In figure 144, we see how the ghost matter propels our matter "forward", accelerating our expansion process. Conversely, we can slow down the expansion of the ghost universe (described with respect to our time t, of course). Thus, the ghost universe acts like a "cosmological constant". Classically, one considers that the cosmological constant corresponds to the repulsive power of the vacuum. In this model, the ghost universe has a "repulsive power", accelerating our expansion.