COSMOLOGY AND GRAVITATION
P.H.R.S. Moraes is M.Sc. in Astrophysics. His expertise area of research is alternative models of gravitation and cosmology. He also teaches Linear Algebra and Vector Calculus at the Engineering College of Guaratinguetá since 2012.
Cosmology is the study of the origin, structure and evolution of the universe. Despite its long time existence, it is still a promising area of science since it adresses some of its greatest mysteries, like the universe composition. In fact, approximately 95% of the universe energy-matter composition is unknown for the scientific community. This amount is though to consist of an exotic fluid named "dark energy", which makes the universe expansion to accelerate and some odd type of matter, which does not interact via electromagnetic force (i.e., it can't be seen), named "dark matter". The remaining 5% compose the stars, galaxies and even ourselves; they are filled by some well known kind of matter, named baryonic matter, from which the atoms are made.
Gravitation is the theory behind a cosmological model. Since Einstein's general relativity publication in 1915, the vast majority of gravitational theories are based on it. To elaborate the theory, Einstein considered the time as a dimension, just like the three well known spatial coordinates (for instance, x, y and z, in cartesian coordinates). Such a consideration give rise to the entity named "space-time", which is curved in the presence of massive bodies.
Nowadays, the most acceptable cosmological model is the Lambda-CDM (Cold Dark Matter), since it presents a great concordance with observations. However, in order to predict the accelerated expansion of the Universe mentioned above, it requires the inception of some sort of quantum vacuum energy permeating it and mathematically described by the Einstein's cosmological constant placed by hand in general relativity field equations. The quantum vacuum energy density might be calculated via cosmology and particle physics. The results obtained from each method are vastly different and consequently the consideration of alternative models of gravitation and cosmology, which in principle does not require the existence of such exotic energy, becomes important.
Alternative models of gravitation vary the form
of describing our Universe. They rise as possible explanations for the inconsistencies of the standard (Lambda-CDM) model (for a brief review on Lambda-CDM inconsistencies beyond the quantum vacuum energy value problem cited above, please click here). As an example of alternative model of gravitation, one could quote the extradimensional models, which consider our Universe as described by five (or even more) rather than four dimensions.
If you want to go further on such subjects, please click on the link my papers so you might know how I have been contributing to advances on theoretical models which describe the Universe.