Can matter accelerate the expansion of the Universe? (I)
Abstract - To the present uncertainties of cosmological measurements, theoretical uncertainties should be added and their potential implications carefully explored. A significant example is provided by the possibility that the expanding cosmological vacuum releases energy in the form of standard matter and dark matter, thus modifying the dependence of the matter energy density with respect to the age and size of our Universe. In this case, if the matter energy density decreases more slowly than in standard cosmological patterns, it can naturally be at the origin of the observed acceleration of the expansion of the Universe without any need for dark energy and a cosmological constant. We illustrate this possible situation using the cosmology based on the spinorial space-time (SST) we introduced in 1996-97. Other scenarios leading to the same effect at the cosmic level are also briefly discussed. (Part I of a contribution to the ICNFP 2016 Conference, July 2016)
Uploaded to Research Gate on April 26, 2016
Nature News wrote recently  "Measurement of Universe's expansion rate creates cosmological puzzle. Discrepancy between observations could point to new physics.", referring to the April 2016 paper by Adam G. Riess and other authors "A 2.4 % Determination of the Local Value of the Hubble Constant" .
Using the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST), Riess et al. announce a best estimate of 73.03+/-1.79 km/sec/Mpc for the present value of the Lundmark Lemaître - Hubble (LLH) constant H (usually called the Hubble constant, but actually due to the work of these three scientists). This result contrasts with previous estimates from other experiments, including Planck.
Riess et al. compare the new obtained value of H with "the prediction of 69.3+/-0.7 km/sec/Mpc with the combination of WMAP + ACT + SPT + BAO" [3, 4] and with the value of 67.3+/-0.7 km/sec/Mpc from CDM and Planck data. To explain the observed differences between the measured values, they con-sider the possibility of an additional source of dark radiation in the early Universe.
Actually, to the present experimental uncertainties theoretical uncertainties should be added. They concern in particular the mathematical structure of space-time, the origin of the Universe, its age and size, the density of matter, the nature and origin of the cosmological constant, the structure and dynamical properties of vacuum, a possible preonic structure...
1.1. The physical vacuum in an expanding universe
If the Universe expands, how does the physical vacuum evolve? How can vacuum adapt itself to this expansion of space?
The answer to these questions will depend crucially on the, by now totally unknown, internal vacuum structure and dynamics.
Attempts to describe the cosmological role of vacuum using standard quantum field theory (QFT) have led to the cosmological constant problem [5, 6]. But as pointed out in previous papers [ 7, 8], the situation can be radically dierent with a preonic vacuum structure naturally avoiding a permanent static presence of the QFT standard condensates [ 9]. If the standard particles are excitations of the physical vacuum, vacuum dynamics can produce them in specific situations and in a way compatible with the successful experimental tests of QFT.
In a preonic vacuum, the Higgs boson and the zero modes of bosonic harmonic oscillators do not need to be permanently materialized, as the vacuum dynamics can generate them when required by the presence of surrounding matter and thus make possible the standard interactions. In this case, the (ground) state of vacuum in regions of the Universe without matter would be substantially dierent from the (excited) one observed in the laboratory.
An important nontrivial information emerges from cosmological data: the physical vacuum appears to be able to naturally expand in space. But the energetic balance of such an expansion remains unknown and can play a crucial role in
the present dynamics of our Universe.
If the expansion of the physical vacuum is energetically favored and particles are vacuum excitations, the evolution of our Universe can lead vacuum to release matter and energy as it expands. This can fundamentally change the dependence of matter energy density with respect to the age and size of our Universe.
Then, matter can be at the origin of the observed acceleration of the expansion of the Universe and no dark energy would be required to produce such an important eect. We present here a simple illustration of this fundamentally new situation, using the cosmology based on the spinorial space-time we introduced in [10, 11]. We also briefly consider other cosmological scenarios leading to the same phenomenon.
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