Quintessence and the Rest of the World: Suppressing Long-Range Interactions (original) (raw)

In this paper, we consider the Universe at the late stage of its evolution and deep inside the cell of uniformity. At these scales, we consider the Universe to be filled with dust-like matter in the form of discretely distributed galaxies, a minimal scalar field, the cosmological constant and radiation as matter sources. We investigate such a Universe in the mechanical approach. This means that the peculiar velocities of the inhomogeneities (in the form of galaxies) as well as fluctuations of other perfect fluids are non-relativistic. Under such conditions, we investigate the theory of scalar perturbations. We show that, at the background level, the considered scalar field has a constant equation of state (EoS) parameter w=−1/3w=-1/3w=−1/3. The fluctuations of the energy density and pressure of this field are defined by the interaction between scalar field background and the gravitational potential of the system. These fluctuations are concentrated around the galaxies screening their gravitat...

A cosmic scalar field evolving very slowly in time can account for the observed dark energy of the Universe. Unlike a cosmological constant, an evolving scalar field also has local spatial gradients due to gravity. If the scalar field has a minimal derivative coupling to electromagnetism, it will cause modifications of Maxwell's equations. In particular, in the presence of a scalar field gradient generated by Earth's gravity, regions with a magnetic field appear to be electrically charged and regions with a static electric field appear to contain electric currents. We propose experiments to detect such effects with sensitivity exceeding current limits on scalar field interactions from measurements of cosmological birefringence. If the scalar field has derivative couplings to fermions, it would also generate observable effects in precision spin precession experiments.

We show that the combined minimal and non minimal interaction with the gravitational field may produce the generation of a cosmological constant without self-interaction of the scalar field. In the same vein we analyze the existence of states of a scalar field that by a combined interaction of minimal and non minimal coupling with the gravitational field can exhibit an unexpected property, to wit, they are acted on by the gravitational field but do not generate gravitational field. In other words, states that seems to violate the action-reaction principle. We present explicit examples of this situation in the framework of a spatially isotropic and homogeneous universe.

In this work, a few models of the Universe which include, in particular, dark energy are presented. In some of them, dark energy is considered to be only a slowly rolling scalar field (quintessence), while in others, its presence is simulated through a negative cosmological constant. The scalar field is minimally coupled to gravity and does not interact with matter, so these models are to be used after decoupling of radiation and matter. However, this ansatz, and a proper normalization, allow to find new general classes of solutions for the cosmological equations. The inclusion of the negative cosmological constant results in the possibility of the future gravitational collapse of the universe; this inclusion solves the horizon problem which prevents the consistent formulation of string theory.