COSMOLOGICAL CONSTRAINT AND ANALYSIS ON HOLOGRAPHIC DARK ENERGY MODEL CHARACTERIZED BY THE CONFORMAL-AGE-LIKE LENGTH
Abstract
We present a best-fit analysis on the single-parameter holographic dark energy model characterized by the conformal-age-like length, 
. Based on the Union2 compilation of 557 supernova Ia (SNIa) data, the baryon acoustic oscillation (BAO) results from the Sloan Digital Sky Survey data release 7 (SDSS DR7) and the cosmic microwave background radiation (CMB) data from the 7-year Wilkinson Microwave Anisotropy Probe (WMAP7), we show that the model gives the minimal 
, which is comparable to 
for the ΛCDM model. The single parameter d concerned in the model is found to be d = 0.232±0.006±0.009. Since the fractional density of dark energy Ωde ~ d2a2 at a ≪ 1, the fraction of dark energy is naturally negligible in the early universe, Ωde ≪ 1 at a ≪ 1. The resulting constraints on the present fractional energy density of matter and the equation of state are 
and 
respectively. We also provide a systematic analysis on the cosmic evolutions of the fractional energy density of dark energy, the equation of state of dark energy, the deceleration parameter and the statefinder. It is noticed that the equation of state crosses from wde > -1 to wde < -1, the universe transits from decelerated expansion (q > 0) to accelerated expansion (q < 0) recently, and the statefinder may serve as a sensitive diagnostic to distinguish the CHDE model with the ΛCDM model.
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