Dark Energy

Professors: Cayon, Cui, Lee, Peterson

Dark Energy is a hypothetical form of energy that permeates all of space and increases the rate of expansion of the universe. Universe is considered to account for 73% dark energy, 23% is dark matter, and 4% is ordinary matter.

The nature of dark energy is one of the most tantalizing mysteries in cosmology today. Observations of high red-shift type Ia supernovae tell us that the expansion of the universe is accelerating at present, which can not be satifactorily explained in the standard cold dark matter scenario. Independent observations of cosmic microwave background and large scale structure tell us that two-thirds of the present density of the universe is composed of some unknown component. The study of this unknown "dark energy" is of the great interest amoung cosmologists today.

Various theoretical models for dark energy have been suggested, the simplest being the cosmological constant model with constant dark energy density and equation of state. Other models include physically motivated models like scalar field quintessence and Chaplygin gas models, as well as geometrically motivated models like scalar-tensor theories and higher dimensional braneworld models.