Abstracts

Emil Nissimov

Quintessence, unified dark energy and dark matter, and gravity-assisted Higgs mechanism

Dark energy and dark matter, occupying around 70% and 25% of the matter content of the Universe, respectively, continue to be the two most unexplained “mysteries” in cosmology and astrophysics. In most loose terms dark energy is responsible for the accelerated expansion of today’s Universe, i.e., dark energy acts effectively as repulsion force among the galaxies - a phenomenon completely counterintuitive w.r.t. naïve notion about gravity as an attractive force. And vice versa, dark matter holds together the matter objects inside the galaxies. The adjective “dark” is due to the fact that both these fundamental matter components of the Universe interact only gravitationally, and they do not directly interact with ordinary (baryonic) matter, in particular, they do not interact electromagnetically and thus they remain “dark”.

There exist a multitude of proposals for an adequate description of dark energy’s and dark matter’s dynamics within the framework of standard general relativity or its modern extensions.

We describe a new type of gravity-matter models where gravity couples in a non-conventional way to two distinct scalar fields providing a unified Lagrangian action principle description of: (a) the evolution of both “early” and “late” Universe - by the “inflaton” scalar field; (b) dark energy and dark matter as a unified manifestation of a single material entity - the “darkon” scalar field. The essential non-standard feature of our models is employing the formalism of non-Riemannian space-time volume forms - alternative generally covariant integration measure densities (volume elements) defined in terms of auxiliary antisymmetric tensor gauge fields. Although being (almost) pure-gauge degrees of freedom, the non-Riemannian space-time volume forms trigger a series of important features unavailable in ordinary gravity-matter models. When including in addition interactions with the electro-weak model bosonic sector we obtain a gravity-assisted dynamical generation of electro-weak spontaneous gauge symmetry breaking in the post-inflationary “late” Universe, while the Higgs-like scalar remains massless in the “early” Universe.