In this talk, we first summarize the successes and issues of the contemporary cosmology. In particular, we focus on the LCDM model in the light of the latest cosmological observations such as the Planck experiment. We then briefly discuss the dark energy concept and the modified gravities as an alternative. The talk will continue with an introduction to a higher dimensional steady-state universe model in dilaton gravity inspired from string theory. We will discuss some aspects of the model in the context of the recent acceleration of the universe and primordial nucleosynthesis. We will see that the model makes successful predictions in cosmology when the action under consideration is reduced to low energy limit of the bosonic string theory with 26-dimensions.
Reference: Ö. Akarsu & T. Dereli, JCAP 02 (2013) 050 [arXiv:1210.8106]