Gravity: fundamental or entropic?
Gravity is usually regarded as a one of four fundamental interactions in Nature. In the beginning of 2010, however, E. Verlinde proposed that gravity is an entropic force, namely the change of entropy leads to gravity. Based on a series of works since 2005, a team leaded by Prof. Rong-Gen Cai at the Institute of Theoretical Physics, CAS, derived the Friedamnn equations describing the evolution of the universe from the point of view of gravity as an entropic force. This work was published in Phys. Rev. D 81:061501,2010 as a Rapid Communication. The group of Prof. Miao Li from the same institute found that the viewpoint of entropic force could also explain the accelerated expansion of the universe, however, another global holographic sreeen has to be introduced in this picture. This work was published in Phys. Lett. B 687:243-247,2010.
Fig. The gravitational field produced by a point mass M can be described by information on the holographic screen. The gravity on the point m comes from the change of information (entropy) on the screen. This figure is taken from the paper by E. Verlinde (arXiv: 1001.0785)