Abstract
To the experimental uncertainties on the present value H 0 of the Lundmark - Lemaitre-Hubble constant, fundamental theoretical uncertainties of several kinds should also be added. In standard Cosmology, consistency problems are really serious. The cosmological constant is a source of well-known diffculties while the associated dark energy is assumed to be at the origin of the observed acceleration of the expansion of the Universe. But in alternative cosmologies, possible approaches without these problems exist. An example is the pattern based on the spinorial space-time (SST) we introduced in 1996-97 where the H t = 1 relation ( t = cosmic time = age of the Universe) is automatically generated by a pre-existing cosmic geometry before standard matter and conventional forces, including gravitation and relativity, are introduced. We analyse present theoretical, experimental and observational uncertainties, focusing also on the possible sources of the acceleration of the expansion of the Universe as well as on the structure of the physical vacuum and its potential cosmological role. Particular attention is given to alternative approaches to both Particle Physics and Cosmology including possible preonic constituents of the physical vacuum and associated pre-Big Bang patterns. A significant example is provided by the cosmic SST geometry together with 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. The SST naturally generates a new leading contribution to the value of H. If the matter energy density decreases more slowly than in standard patterns, it can naturally be at the origin of the observed acceleration of the expansion of the Universe. The mathematical and dynamical structure of standard Physics at very short distances can also be modified by an underlying preonic structure. If preons are the constituents of the physical vacuum, as postulated two decades ago with the superbradyon (superluminal preon) hypothesis, the strongest implication would be the possibility that vacuum actually drives the expansion of the Universe. If an unstable (metastable) vacuum permanently expands, it can release energy in the form of conventional matter and of its associated kinetic energy. The SST can be the expression of such an expanding vacuum at cosmic level. We briefly discuss these and related issues, as well as relevant open questions including the problematics of the initial singularity and the cosmic vacuum dynamics in a pre-Big Bang era. The possibility to obtain experimental information on the preonic internal structure of vacuum is also considered.
Highlights
What is the "trouble with H0" recently considered by several authors [1]? Nature News wrote on April 2016 [2] "Measurement of Universe’s expansion rate creates cosmological puzzle
Using the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) [4], Riess et al announce a best estimate of 73.24±1.74 km/sec/Mpc for the present value H0 of the Lundmark - Lemaître - Hubble (LLH) constant H
It clearly turns out that the observed acceleration of the expansion of the Universe does not require the introduction of the standard cosmological constant with the usual dark energy, and that simpler and more natural mechanisms can be at work
Summary
What is the "trouble with H0" recently considered by several authors [1]? Nature News wrote on April 2016 [2] "Measurement of Universe’s expansion rate creates cosmological puzzle. To the present experimental and observational uncertainties, basic theoretical puzzles and unknowns 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. Alternative cosmologies involving pre-Big Bang scenarios and incorporating new physics can naturally avoid the conventional Big Bang and cosmic inflation [13, 14] This contribution is devoted to alternative approaches to some basic questions in Cosmology and Particle Physics, with particular emphasis on space-time and on the possible internal structure of the physical vacuum (see [15]). The potential implications of new physics, including superluminal preons as fundamental vacuum constituents, together with a pre-Big Bang era, are given particular attention including the question of a possible initial singularity
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