...The system (27-a) and (27-b) gives a non-symmetrical evolution history of coupled universes. In reference [6] is developped a model in which the so-called constants of physics are "time-dependant". See figure 5.

Fig.4 : Evolution of the so-called constants of physics.

...This work followed previous works ( [10] , [11] , [12] ). It provides another observational confirmation, as mentioned first in reference [7] : the cosmological horizon does not vary like the cosmic time t any longer for c varies. We get :
(28)

Horizon = R(t)

which ensures the homogeneity of the universe at any time. This theory matches the inflation's theory of Linde.
In addition, 2d numerical simulations showed that, when interacting with its twin structure, a galaxy forms barred spiral structure, so that we get an alternative interpretation of the phenomenon, in terms of interaction of the galaxy with "irs image" in the twin universe. In reference[7] we showed that the model gives an alternative interpretation to strong gravitational lensing effects, interpreted in terms of "negative lensing effect".

.

4 - The twin universe : how does it look like ?

... The twin universe model explains the Very Large Structure of the universe. The Jeans time varies like the inverse root of the mass-density. As the twin universe is denser, it undergoes gravitational instability first, after discoupling with radiation, forms clumps and repels our matter, which takes place in the remnant place. See figure 5.

Fig.5 : Twin universe and our universe : conjugated VLS structures.

...On the right : what we can observe, optically. Left : the twin universe structure. On figure 6, the two, combined.

Fig.6 : The two, combined.

...As we see, twin matter clumps are located at the center of the cells, and keep ordinary matter at distance. By the way (see reference [7] ) it provides an interesting model for galaxies' formation. If someone could travel in the cruise universe, he would just see the distant clumps. They can be compared to some giant proto-stars, with quasi-infinite cooling time. They emit eletromagnetic energy corresponding to red and infrared light. If it does exist, the twin universe would be fairly different from ours : it would not contain stars, planets, like ours. It is just filled by these huge "proto-stars", made of hydrogen and helium. Life would not be present in the twin universe.

5 - Natural hyperspace transfer.

...But it is not the subject of the present paper, devoted to the problem of interstellar travel's problem.
What is the link ?

...As we can see in section 2, the velocity of the light c* , in the twin space, can be fairly different from the one of our own universe. c* could be 50 times higher than c. If we could find a way to be "transfered" in the twin space, we could cruise in it, using this twin space as some express subway.

...In physics, many "artificial phenomena", due to human activity can be linked to similar natural phenomena. Example : fusion. We experience "artuficial fusion" in H-bombs. But nature did it naturally billions tears ago and the process continues in stars. Another example : shock waves. We know how to create shock waves with airplanes, or guns. Nature makes shock waves with lightnings, thunderbolts (due to thermal effect). If hyperspace transfer could become possible, from our space to the twin space, we can think natures experiences it "naturally".
...Almost all scientists believe in black hole's existence. But it is not experimentally proved. The study of the dynamics of the centers of many galaxies suggests that "giant black holes" could lie there. But X-ray observations showed that such giant black holes (million solar masses) were strangely "silent".
...We have very few candidates for "ordinary" black holes coupled to ordinary stars, and they are fairly distant. Everybody knows that the measure of distances to stars is still very questionable. See for example the recent critics abour Hipparcos' data. A slight variation of the distance to a binary system in which one thinks that one element would be a black hole would transform this last in a simple neutron star, which emits X-rays too.
...Black hole is a question of belief. The majority of scientists believes in the existence of black holes, small or giant, nothing else.If somebody shows some skepticism, they answer :

- What do you suggest ? Do you have a challenger theory ? What could be the fate of a neutron star which overcomes its limit of stability ? (close to 2.5 solar masses).

...Personnaly I think that when a neutron star overcomes its limit of stability, an hypertoric bridge forms at its center, matter flows through. It can be a soft phenomenon, in the case of a neutron star which reaches the critical mass value by continous matter transfer from a companion star. This idea is presented in my website ("questionable black hole"). The starting point is the study of Tolmann, Oppenheimer and Volkov ( [13] and [14] ). One builds a state equation for a constant density neutron spherically symmetric neutron star. The specialist knows that the geometry of steady dense spherically symmetric objects can be described by two linked metrics, called external and internal Schwarzschild metrics. The external Schwarzschild metric is :
(29)

while the internal corresponds to
(30)

...Both become "pathological" for the same value of the radius, corresponding to the Schwarzschild radius. On figure 7 a schematic description of a subcritical neutron star.

Fig.7 : Subcritical neutron star.

...In gray : the neutron star. Inside : the Schwarzschild radius (the one, for the sun, is 2.7 kilometers).Outside an external critical radius, which only depends on the value of the density of the material, which can be considered as constant, so that this dotted sphere is fixed when the mass of the star is increased. The figure 8 shows the rise to "geometrical criticities", which involve the two metrics. Geometrical criticity occurs for the same value of the radius.

Fig.8 : Geometrical criticity.

which is the Schwarzschild radius :
(31)

r is the (constant) mass density inside the neutron star. c is the velocity of the light. r_n is the radius of the star. The next equation (from reference [13] ) is the TOV equations, state equation describing the interior of a neutron star :
(32)

...Now, we can compare the caclculated pressure, following this classical TOV model, for different values of the neutron star radius.

Fig.8 : Evolution of the pressure inside a neutron star, for increased values of its external radius.

...For moderate values of the radius, say < 0.9 r crit the pressure varies slowly. But, suddently, when the radius approaches a new critical value :
(33)

r _crit = 0.9429 R_s

the pressure becomes infinite at the center, so that this physical criticity occurs before the classical geometrical criticity. Few attention was paid to this important point since more than the half of a century.

...The growth of the mass of a neutron star is supposed to be at first a physical problem, not a pure geometrical and mathematical problem. Before thinking about geometrical criticity, we have to face a first question :

- What happens when the pressure becomes infinite at the center of a neutron star ?

...In several papers, and specially [7] I have developped a model where the constants of physics depends on the energy density, which corresponds to figure 4. As we can see, when the energy density becomes infinite (and a pressure is a energy density) the velocity of the light becomes infinite. All the constants are strongly altered. I think a similar phenomenon could occur at the center of a neutron star, when it approaches physical criticity. A bridge could form, linking the two folds of the universe, and making possible mass transfer from our fold to the other one. A rough caclculation shows that a very small "space bridge", as large as a tiny ball, could evacuate, due to the extremely high mass-density and relativistic velocity, a mass flux corresponding to the solar wind of a companion star, if absorbed by the neutron star.
...If this idea is valid, such phenomenon would automatically keep neutrons stars beyond geometrical criticity. The system would work like the plughole of a bath. The next images are didactic images of the process.

Fig.9 : Didactic image of a subcritic neutron star, coupled to a companion star.

Fig.10 : Didactic model of our model, challenger to the black hole model :
Extra matter would be evacuated in twin space through a space bridge.

...