Ru-Keng Su

Testing the viability of the interacting holographic dark energy model by using combined observational constraints

Using the data coming from the new 182 gold type Ia supernova samples, the shift parameter of the cosmic microwave background given by the three-year Wilkinson Microwave Anisotropy Probe observations, and the baryon acoustic oscillation measurement from the Sloan digital sky survey, H(z) and lookback time measurements, we have performed a statistical joint analysis of the interacting holographic dark energy model. Consistent parameter estimations show us that the interacting holographic dark energy model is a viable candidate for explaining the observed acceleration of our universe.

Constraints on the dark energy from the holographic connection to the small l CMB suppression

Abstract Using the recently obtained holographic cosmic duality, we reached a reasonable quantitative agreement between predictions of the cosmic microwave background radiation at small l and the WMAP observations, showing the power of the holographic idea. We also got constraints on the dark energy and its behaviour as a function of the redshift upon relating it to the small l CMB spectrum. For a redshift independent dark energy, our constraint is consistent with the supernova results, which again shows the correctness of the cosmic duality prescription. We have also extended our study to the redshift dependence of the dark energy.

Constraints on dark energy from holography

Using the holographic principle we constrained the Friedmann equation, modified by brane-cosmology inspired terms which accommodate dark energy contributions in the context of extra dimensions.

Observational constraints on the dark energy and dark matter mutual coupling

Abstract We examine different phenomenological interaction models for Dark Energy and Dark Matter by performing statistical joint analysis with observational data arising from the 182 Gold type Ia supernova samples, the shift parameter of the Cosmic Microwave Background given by the three-year Wilkinson Microwave Anisotropy Probe observations, the baryon acoustic oscillation measurement from the Sloan Digital Sky Survey and age estimates of 35 galaxies. Including the time-dependent observable, we add sensitivity of measurement and give complementary results for the fitting. The compatibility among three different data sets seem to imply that the coupling between dark energy and dark matter is a small positive value, which satisfies the requirement to solve the coincidence problem and the second law of thermodynamics, being compatible with previous estimates.

Relating Friedmann equation to Cardy formula in universes with cosmological constant

Abstract A relation between the Friedmann equation and the Cardy formula has been found for de Sitter closed and anti-de Sitter flat universes. For the remaining (anti)-de Sitter universes the arguments fail, and we speculate whether the general philosophy of holography can be satisfied in such contents.

Holographic explanation of wide-angle power correlation suppression in the cosmic microwave background radiation

We investigate the question of the suppression of the CMB power spectrum for the lowest multipoles in closed Universes. The intrinsic reason for a lowest cutoff in closed Universes, connected with the discrete spectrum of the wavelength, is shown not to be enough to explain observations. We thus extend the holographic cosmic duality to closed universes by relating the dark energy equation of state and the power spectrum, showing a suppression behavior which describes the low l features extremely well. We also explore the possibility to disclose the nature of the dark energy from the observed small l CMB spectrum by employing the holographic idea.

FRIEDMANN EQUATION AND CARDY FORMULA CORRESPONDENCE IN BRANE UNIVERSES

We study the brane with arbitrary tension σ on the edge of various black holes with AdS asymptotics. We investigate Friedmann equations governing the motion of the brane universes and match the Friedmann equation to Cardy entropy formula.

Hawking radiation in a d -dimensional static spherically symmetric black hole surrounded by quintessence

We present a solution of Einstein equations with quintessential matter surrounding a d-dimensional black hole, whose asymptotic structures are determined by the state of the quintessential matter. We examine the thermodynamics of this black hole and find that the mass of the black hole depends on the equation of state of the quintessence, while the first law is universal. Investigating the Hawking radiation in this black hole background, we observe that the Hawking radiation dominates on the brane in the low-energy regime. For different asymptotic structures caused by the equation of state of the quintessential matter surrounding the black hole, we learn that the influences by the state parameter of the quintessence on Hawking radiation are different.

Quasinormal modes in pure de Sitter spacetimes

We have studied scalar perturbations as well as fermion perturbations in pure de Sitter spacetimes. For scalar perturbations we have shown that well-defined quasinormal modes in d-dimensions can exist provided that the mass of scalar field m>(d-1/2l). The quasinormal modes of fermion perturbations in three and four dimensional cases have also been investigated. We found that different from other dimensional cases, in the three dimensional pure de Sitter spacetime there is no quasinormal mode for the s-wave. This interesting difference caused by the spacial dimensions is true for both scalar and fermion perturbations.

DYNAMICS AND HOLOGRAPHIC DISCRETENESS OF TACHYONIC INFLATION

We consider issues related to tachyonic inflation with inverse-power-law potential. We find the solution of the evolution equations in the slow roll limit in FRW as well as in the brane cosmology. Using the holographic entropy bound, we estimate the quantum-gravitational discreteness of tachyonic inflation perturbations.