Energy sinks

In Cosmology, the energy sinks is a hypothetical form of energy filling all the Univers and exerting a negative Pression behaving like a force repulsive Gravitation nelle. The energy sinks could explain the Accélération of the expansion of the universe and the cosmological Constante. The purpose of current research Astrophysique S on the subject is principal to measure with precision the expansion of the universe in order to determine the way in which the expansion varies with time. The universe would be composed of it to approximately 65%.

Origin

Dark energy (not to be confused, as it is often the case, with the matter sinks) is a concept directly connected to the constant cosmological $\ lambda$ . The latter appears in the second member of the equation of Einstein “modified”: $G_ {\ alpha \ beta} = 8 \ pi T_ {\ alpha \ beta} + \ Lambda g_ {\ alpha \ beta}$

This constant was added by Albert Einstein to his primitive equation to make it possible a static universe to satisfy it (it will be proven thereafter that the static universe of Einstein is unstable). It introduces a kind of energy (a scalar Champ constant) present in any point of the space-time continuum, which, with a suitable choice of sign and value, can be opposed to gravity and modify the profile of evolution of the “size of the universe” (scale factor in the metric FLRW).

During discovered expansion of the universe (cf Edwin Hubble), Einstein disavowed this wart (“ the most obvious error of my life ”) with the profit of the original equation (where $\ Lambda$ does not appear), considered to be more “esthetic” and in conformity with the observations of the time. Until in the years 1980, the cosmological constant was more or less ignored in “conventional” cosmology.

In the Années 1970, Alan Guth has advanced that the cosmological constant would cause cosmic inflation in the paramount universe (via a model of Lemaître of “hesitant” universe). This theory was abandoned with the profit of the models inflationnaires.

Birth of the concept of energy sinks

At the end of the Years 1990, the satellites and the telescopes allowed very precise measurements of the distant Supernova S and fossil Rayonnement microwave. Several characteristics observed, in particular the acceleration of the Expansion of the universe, result in supposing that there exists indeed a kind of energy (baptized sinks ) whose equation of state would violate the strong version of the principle of energy, i.e.: $3 P + \ rho > 0$ , but not its released version $P + \ rho > 0$ . An energy which would violate the two principles is called phantom energy.

Because of its repulsive nature, the energy sinks tends to accelerate the Expansion of the universe, rather than to slow down it, like the “normal” Matière does it. An accelerating universe is exactly what one notes by observing the most remote supernovæ. In a remarkable way, these observations seem to indicate that dark energy must account for approximately 70% of the density of energy. Thus, while adding various energies, one arrives exactly so that it is necessary to have a universe of quasi-null curve, which corresponds to the current observations (2007).

Nature of energy sinks

The true nature of dark energy largely forms part of the field of the speculation. Some estimate that energy sinks would be the energy of the quantum vacuum, modelled by the constant cosmological of the General relativity. It is the simplest explanation and to pose a constant cosmological means that the density of dark energy is uniform, and constant in all the universe, invariable according to time. It is the form introduced by Einstein, and this form is coherent with our current observations of the universe. If the energy sinks takes this form, that means that it is about a fundamental property of the universe.

Other assumptions were advanced. Thus, the energy sinks could be induced by the existence of particle S unknown factors. These models are called Quintessence. Certain theories affirm that these particles were created in sufficient quantity at the time of the Big bang to fill all space. Nevertheless, if that were the case, one would expect that they gather, in the same way that ordinary matter, and one would observe variations of density according to time. No proof was observed by it, but the precision of the observations does not make it possible to exclude this assumption.

Inflation

Implications on the destiny of the Universe

If the energy sinks continuous to dominate the energy balance of the universe, the expansion observed of space will continue to accelerate. The structures which are not gravitationally dependant will end up moving away from/to each other at apparent speeds higher than that of the light. Thus, this acceleration will finally prevent us from observing important portions of the universe which is visible today; our cosmological horizon, rather than to move back, will end up approaching us.

If the density of dark energy does not increase, the existence of the systems bound by the gravitation, the such galaxies or the planetary systems, is not threatened. Thus the Solar system or the Milky Way will remain primarily identical so that they are today, whereas the remainder of the universe, beyond our local supercluster, seems to move away constantly.

On the other hand, if dark energy increases with the time, one finds oneself in a scenario of the type Big RIP, where all the matter of the universe, until in its same atoms, would disintegrate, leaving an infinite and completely empty universe.

Finally, dark energy could be diluted with time, to be even reversed. Uncertainties on the observations leave the open door on the fact that the Gravité can one day dominate a universe, which would contract then on itself and disappears in a Big Crunch. This scenario nevertheless is regarded as the least probable.

In May 2004, the publication of work completed with the satellite Chandra and consisting in measuring the distances from 26 remote galaxy clusters seems to confirm that the expansion started to accelerate there is 6 billion years, and that dark energy seems to remain constant, or then varies very slowly. These results are toutesfois in dissension with those obtained by the European sattelite XMM.

That is compatible with the existence of a cosmological constant and returns the scenario of the very improbable Big Crunch.

Internal bonds

Table of the astrophysical constants
Energy of the vacuum
Quintessence

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