"…Through the Labyrinth of Cosmology"
Abstract: Cosmology is certainly one of the most active research areas in physics, and presumably the main reason is the lack of a convincing explanation for the observed accelerated expansion of the universe at the level of fundamental physics. The possible explanations of this large scale property also lead to reconsider some reliable models of the early universe. The standard model of cosmology, LCDM model, is the ‘best-fit’ model to explain this observation together with the explanation of the Cosmic Microwave Background Radiation and the amount of baryonic matter in the universe, in the context of Einstein’s General Relativity. On the other hand, almost 95% of the matter-energy content of this model is composed of only-gravitationally observable “dark” components. This huge amount of darkness=ignorance reminds physicists to seek alternatives to the LCDM model, ranging from introducing some other ‘weird’ matter components into the model to ‘alternative gravity’ theories to General Relativity, or both. Interestingly many of these new suggestions/alternatives work succesfully in one way or another, which is another curious point worth examining. Then it is natural to ask whether these seemingly different models/suggestions can be grouped and sorted in a way to give us a clue about the ultimate model to explain the universe consistently and satisfactorily. In this talk, I would like to discuss whether this kind of classification is possible for these apparently different models (inspired by the phenomenon of Universality Classes in physics) by considering them as dynamical systems through their critical points and their behaviour about these critical points.