Probing the course of cosmic expansion with a combination of observational data

Abstract

We study the cosmic expansion history by reconstructing the deceleration parameter q(z) from the SDSS-II type Ia supernova sample (SNIa) with two different light curve fits (MLCS2k2 and SALT-II), the baryon acoustic oscillation (BAO) distance ratio, the cosmic microwave background (CMB) shift parameter, and the lookback time-redshift (LT) from the age of old passive galaxies. Three parametrization forms for the equation of state of dark energy (CPL, JBP, and UIS) are considered. Our results show that, for the CPL and the UIS forms, MLCS2k2 SDSS-II SNIa+BAO+CMB and MLCS2k2 SDSS-II SNIa+BAO+CMB+LT favor a currently slowingdown cosmic acceleration, but this does not occur for all other cases, where an increasing cosmic acceleration is still favored. Thus, the reconstructed evolutionary behaviors of dark energy and the course of the cosmic acceleration are highly dependent both on the light curve fitting method for the SNIa and the parametrization form for the equation of state of dark energy. PACS numbers: 95.36.+x, 98.80.Es

Quantization of the universe as a black hole

“…These two predictions are very well satisfied by observations of Akarsu and Dereli (2011) and Li et al (2010). They imply symmetry in the function q(x) such that our present age, where the earth is populated by the human race, is twice the age at which the acceleration of the expansion of the universe was zero.…”

“…Then the integral of (4) between 0 and 1 is inevitably the condition (5). Back in time the expected value for q 1 = q(0) after inflation, and very near the initial stages, should be found as a limiting process (Li et al 2010) and is close to 0.5 (at a very high red shift). The present value of q is roughly about q 0 ≈ −0.5.…”

“…From (12) we see that this condition implies for q the initial value q = −q 0 ≈ 0.5. Given that this must have occurred during a very short period of time, as is the case for inflation, the expected value for q after inflation, and very near the initial stages, should be found as a limiting process (Li et al 2010) and it is in fact close to 0.5. In Fig.…”

Expanding Universe: slowdown or speedup?

“…Moreover, obtain a convincing result one will probably have to remake all the data treatment procedure. Thus it was shown in [58,59] that there is a contradiction between the data obtained from (SNe Ia+BAO) for small redshifts and those from (CMB) for high ones. The contradiction is in the fact that the analysis of two data sets separately one obtains opposite results.…”

“…Besides that the data set concerning supernovae with moderate red shift (z < 0.3) was remarkably extended. Today there are several works [58,59], making analysis of the above mentioned data in order to test the transient acceleration hypothesis. All the authors share common opinion that the ultimate answer will be given only by remade more accurate measurements.…”