The Dark Side of the Universe: Dark Energy, Dark Matter and Modified Gravity

Dear Colleagues,

Modern astrophysical and cosmological models are plagued with two severe theoretical problems, namely, the dark energy and the dark matter enigmas. Relative to the latter, the dynamics of test particles around galaxies, as well as the corresponding mass discrepancy in galactic clusters, is explained by postulating the existence of a hypothetical form of matter, called dark matter. Relative to the dark energy problem, high precision observational data has confirmed with startling evidence that the Universe is undergoing a phase of accelerated expansion. This phase is one of the most important and challenging current problems in cosmology, and represents a new imbalance in the governing gravitational equations. Several candidates, responsible for this expansion, have been proposed in the literature, in particular, dark energy models and modified theories of gravity, amongst others. Outstanding questions are related to the nature of this so-called “dark energy” that is driving the acceleration of the universe, and whether it is due to the vacuum energy or a dynamical field. On the other hand, the late-time cosmic acceleration, as well as the elusive dark matter, may be due to modifications of General Relativity, which introduce new degrees of freedom to the gravitational sector itself.

This Special Issue will explore a plethora of viable dark matter, dark energy and modified gravity models, some of which consistently reproduce the inflationary epoch, and will be tested against large-scale structure and lensing, astrophysical and laboratory measurements, as well as laboratory and space-based Equivalence Principle experiments. These Solar System tests, large scale structure measurements and lensing data, amongst others, restrict the range of allowed modified gravity models and offer a window into understanding the perplexing nature of the cosmic acceleration and of gravity itself.

Dr. Tiberiu Harko
Dr. Francisco S. N. Lobo
Guest Editors

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