Quantum Vacuum and the Universe - An Emerging Cosmological Model

This book "Quantum Vacuum and the Universe - An Emerging Cosmological Model" is a first, basic and pedagogical presentation, of a new cosmological model based on the working hypothesis that quantum vacuum fluctuations are virtual gravitational dipoles. 

     Our current understanding of the Universe is both, a fascinating intellectual achievement and the source of the greatest crisis in the history of physics.  In brief, sophisticated astronomical observations have revealed a series of phenomena that are a complete surprise and a complete mystery for contemporary physics.

• In galaxies and clusters of galaxies, the gravitational field is much stronger than it should be according to our theory of gravitation and the existing amount of the Standard Model matter (i.e. matter composed from quarks and leptons interacting through the exchange of gauge bosons).
• The expansion of our Universe is accelerating; contrary to the common sense expectation that gravity must decrease the speed of expansion.
• Our Universe (with the exception of the quantum vacuum) is dominated by matter; apparently, in the primordial Universe, something has forced the matter-antimatter asymmetry.
• If it exists, the gravitational impact of the quantum vacuum is many orders of magnitude smaller than predicted by contemporary theoretical physics; a phenomenon known under the name “the cosmological constant problem”.
• The Big Bang model has inherent problems: the problem of the initial singularity and the fact that it contradicts some observations (in particular the observed level of homogeneity and isotropy of the Cosmic Microwave Background).

     The scientific reaction to the above problems can be summarized in two sentences. First, there is a consensus that these phenomena cannot be explained in the framework of General Relativity and the Standard Model of Particles and Fields.  Second, each problem has been considered separately from the others; hence, the number of the invoked ad-hoc hypotheses is equal to the number of problems.

     In order to explain observations, besides Standard Model matter, we have filled the Universe with hypothetical dark matter and dark energy, while in the primordial Universe we have assumed the existence of a mysterious inflation field (that causes a monstrous initial expansion of the Universe with speed many orders of magnitude greater than the speed of light) and an enormous CP violation of unknown nature. And, after all these hypotheses, we still have no plausible idea what is at the basis of the cosmological constant problem. We do not know if our hypotheses are correct or just well mimic something that we didn’t understand. In any case, the current theoretical thinking is a departure from the traditional elegance, simplicity and beauty of theoretical physics.

     In sharp contrast with the dominant paradigm, this book presents a unique attempt to explain the observed phenomena in the framework of well-established physics. In the first Chapter of this book we give a rudimentary overview of two cornerstones of contemporary physics (the Standard Model of Particles and Fields and General Relativity) and their apparent inability to produce a model of the Universe in agreement with observations. After that we show that a single hypothesis that “quantum vacuum fluctuations are virtual gravitational dipoles” offers fundamental physics the potential to explain the greatest mysteries of our time: what is the nature of what we call dark matter, what is the nature of what we call dark energy and why matter dominates antimatter in the Universe. According to this emerging model of the Universe, the only matter-energy content of the Universe is Standard Model matter. The phenomena usually attributed to hypothetical dark matter, may be considered as a consequence of the local gravitational polarization of the quantum vacuum by the immersed baryonic matter within it; i.e. the galactic halo of dark matter can be replaced by the halo of the polarized quantum vacuum.  Globally “quantum vacuum” may be viewed as a cosmological fluid, which during expansion of the Universe converts from a fluid with negative pressure - allowing an accelerated expansion of the Universe - to a fluid with zero pressure, which physically means the end of the accelerated expansion. This, for the first time, suggests that the quantum vacuum may explain both phenomena; phenomena for which we have invoked dark matter and phenomena for which we have invoked dark energy. Furthermore, as a consequence of the hypothesis of virtual gravitational dipoles, together with the gravitational version of the Schwinger mechanism, the possibility exists that we live in a cyclic universe with cycles alternatively dominated by matter and antimatter. Consequently, at least mathematically, there is no initial singularity, there is no need for cosmic inflation and there is an elegant explanation of the matter-antimatter asymmetry in the universe: our universe is dominated by matter because the previous cycle was dominated by antimatter (and the next cycle would be dominated by antimatter again). 

     For a fair understanding of this book the knowledge at the level of a Bachelor’s in physics or astrophysics is needed. However, we have tried to write this book in such a way that readers unable to follow mathematics still can understand at a popular level.

     While we have tried to make a reader-friendly presentation based on intuition, counterintuitive places are unavoidable in any book of modern physics. Our common sense (which is result of our everyday perception and interaction with our neighbourhood) was a powerful tool in the development of classical physics; classical physics and common sense were in full harmony, in a kind of symbiosis.  However, we are many orders of magnitude bigger than quarks and leptons, and many orders of magnitude smaller than the Universe. It shouldn’t be surprising that the laws of classical physics (and with them our common sense) are not valid at so different scales of size, speed and mass. Hence, it is natural that there is a conflict between our common sense and the most fundamental laws of nature. We mustn’t be inflexible; our job is not to impose our classical common sense on nature but to understand what the common sense of nature is.

     The hope is that in addition to its scientific value (which cannot be estimated before the appropriate experiments and astronomical observations) this book would stimulate imagination and diversity of ideas and be a voice opposing the prescribed truth, uniform thinking and industrialization of the fundamental research.