Dark Energy as a Signature of Extra Dimensions.pdfVIP

a r X i v : a s t r o - p h / 0 5 0 1 3 6 7 v 2 1 9 J a n 2 0 0 5 Dark Energy as a Signature of Extra Dimensions B. Li,1, ? M. -C. Chu,1, ? K. C. Cheung,1 and A. Tang1 1Department of Physics, The Chinese University of Hong Kong, Hong Kong SAR, China (Dated: February 2, 2008) Abstract One of the most important and surprising discoveries in cosmology in recent years is the realiza- tion that our Universe is dominated by a mysterious dark energy, which leads to an accelerating expansion of space-time. A simple generalization of the standard Friedmann-Robertson-Walker equations based on General Relativity and the Cosmological Principles with the inclusion of a number of closed extra dimensions reproduces the currently observed data on dark energy, without the introduction of any cosmological constant or new particles. In particular, with a few extra dimensions, we obtain the redshift dependence of the deceleration parameter, the dark energy equation of state, as well as the age of the Universe in agreement with data, with essentially no free parameter. This model predicts that the extra dimensions have been compactified throughout the cosmic history, and it therefore suggests that signals from early Universe may give promising signatures of extra dimensions. ?Email address: bli@phy.cuhk.edu.hk ?Email address: mcchu@phy.cuhk.edu.hk 1 Recent advances in cosmological observations produce a large set of high quality data from which an unprecedented detailed knowledge of the universe can be extracted. Furthermore, a ′cosmic concordance′[1] has emerged from several different and independent observations such as Type IA supernovae [2, 3], cosmic microwave background (CMB) anisotropies [4] plus large scale galaxy surveys [5] and Sachs-Wolfe effects [6], pointing to a universe with flat space-time dominated by a mysterious dark energy, which accounts for about 70% of the total energy content. The remaining 30% contribution is largely due to dark matter. Furthermore, the dar