Holographic Energy And Holographic Description Of The Universe

In this thesis, we reviewed the current situation of the study about the darkenergy and introduced the holographic dark energy model in detail. Based onthe results of the former exploiters, we made further research on the holographiccharacteristics of the energy in the universe and gave viewpoints of ourselves.This thesis comprises three parts. In the first part, we study the stabilityof the holographic dark energy model under perturbation in the closed universe;in the second part, a holographic EKMR model is suggested (EKMR stands forthe total energy coming from spacial curvature, matter and radiation together), then, a holographic description of the universe is given; in the third part, thestability of the holographic description of the universe is also investigated.Part I: we study the evolvement of the perturbation in closed universe byusing the perturbed Einstein equation and considering the scalar perturbationof the FRW metric, we find that the perturbation is a decaying mode not onlyin supper-horizon mode but also in sub-horizon mode, which denotes that theholographic dark energy model in closed universe is stable and is a support ofthis model.Part II: the holographic principle is a basic principle in theoretical physicswhich is thought to be manifest in an underlying quantum theory of gravity, sucha basic principle should have the property of universality, thus, since the darkenergy has already shown its holographic characteristic, the remnant energy inthe universe should also have their holographic nature. Motivating by this pointof view, we suggest the holographic EKMR model. According to this model, thetotal energy coming from spacial curvature, matter and radiation together is holo-graphic and can be obtained by using the particle horizon for the infrared cut-o?.Combining these two holographic energy models, we can now give a holographicdescription of the universe that (1) our universe is holographic and is composedof two holographic components, its evolvement depends on the evolvement of thetwo components and (2) a given universe must have both the dark energy andEKMR as long as it has the two horizons.Part III: we study the stability of the holographic description of the uni-verse. Analogous to the first part, we investigate the evolvement of the perturba- tion coming from holographic dark energy and holographic EKMR by using theperturbed Einstein equation and considering the scalar type perturbation of theFRW metric, we find that the perturbation is decaying mode not only in supper-horizon mode but also in sub-horizon mode, which denotes that the holographicdescription of the universe is stable and is a support of this description.