Cosmology

The most ancient branch of science is probably Cosmology (from the Greek: kosmos, Universe, world, order and logos, word, theory). Early civilizations used their own cosmological models to establish the seasons and made detailed astronomical observations that were very useful to predict periodic phenomena like rainy seasons and periods of droughts. The knowledge about the kosmos was increased through the centuries but quantitatively our understanding did not go further than to give orders of magnitude estimates of the quantities involved. Nevertheless, observations have quickly improved and became more accurate in the last three decades allowing us to obtain better measurements of the basic cosmological parameters. We have entered the era of precision cosmology where the observables have been determined within a few percent accuracy. The data are well accommodated within the framework of the Standard Cosmological Model or Concordance Model, based on the Big Bang Theory together with the inflationary paradigm. The model explains the evolution of the Universe from the first fractions of a second to the present day. The Concordance Model is based on General Relativity (GR) and is supported by three main observations: the expansion of the Universe, discovered by E. P. Hubble, the relative abundance of light elements, explained by G. Gamow and the Cosmic Microwave Background radiation, discovered by A. A. Penzias and R. W. Wilson. Each of these four elements dates back to at least fifty years. In the last two decades new observational data have emerged, confirming the model further but also have pointed out some shortcomings that question if GR is the effective theory of gravity.

Is GR sufficient to explain all the gravitational phenomena from collapsed objects to the evolution of the Universe and the formation of structures? Does the theory need to be changed, or at least, modified? These are still open questions and two main approaches have been taken: (A) preserve the success of GR by incorporating new particles and/or scalar fields not yet observed and improve the accuracy of the data to verify the model further and (B) modify the theory of gravity to make it compatible with Quantum Mechanics and cosmological observations without introducing additional particles and fields.

In the area of Cosmology, I have been investigating the following topics:

• Dark Energy

• Variation of fundamental constants