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arXiv 1307.4552astro-ph.CO
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经典的幂律宇宙学:暗能量状态方程

Quintessential power-law cosmology: dark energy equation of state

Burin Gumjudpai

摘要:

研究了标度因子为宇宙时间的幂次方的幂律宇宙学$a \propto t^{\a}$。我们回顾并讨论了从各种类型的观察中获得的$\a$的价值。从$z < 0.5$出发,考虑宇宙晚期暗能量占主导地位的时代,利用宇宙微波背景辐射(WMAP 7)、重子声振荡(BAO)和哈勃观测数据的观测推导结果,求出了幂指数$\a$等宇宙学变量。发现$\a$是$0.99 \pm 0.02$(WMAP 7 +BAO+ $H_0$)和$0.99 \pm 0.04$(WMAP 7)。这些值并不排除在1 $σ$加速的可能性,因此一般来说,幂律宇宙学是可行的。在考虑正则标量场暗能量与幂律宇宙学的情况下,我们导出了标量场势、标量场精确解和状态方程参数。我们发现,包含动力学正则标量场的幂律宇宙学方案预言了当前的状态方程参数$w_{ϕ, 0} = -0.449 \pm 0.030 $,而使用WMAP 7数据的$w$ CDM(模型无关,$w$常数)允许$w_{ϕ, 0}$的最大(+1 $σ$)值为-0.70,超出了预测范围。然而,在改变$w_ϕ$的情况下,从典型幂律宇宙学预测的$w_{ϕ, 0}$值允许在1 $σ$不确定度内。

英文摘要:

Power-law cosmology with scale factor as power of cosmic time, $a \propto t^{\a}$, is investigated. We review and discuss value of $\a$ obtained from various types of observation. Considering dark energy dominant era in late universe from $z < 0.5$, we use observational derived results from Cosmic Microwave Background (WMAP7), Baryon Acoustic Oscillations (BAO) and observational Hubble data to find power exponent $\a$ and other cosmological variables. $\a$ is found to be $0.99 \pm 0.02$ (WMAP7+BAO+$H_0$) and $0.99 \pm 0.04$ (WMAP7). These values do not exclude possibility of acceleration at 1$σ$ hence giving viability to power-law cosmology in general. When considering scenario of canonical scalar field dark energy with power-law cosmology, we derive scalar field potential, exact scalar field solution and equation of state parameter. We found that the scenario of power-law cosmology containing dynamical canonical scalar field predicts present equation of state parameter $w_{ϕ, 0} = -0.449 \pm 0.030 $ while the $w$CDM with WMAP7 data (model independent, $w$ constant) allows a maximum (+1$σ$) value of $w_{ϕ, 0}$ at -0.70 which is off the prediction range. However, in case of varying $w_ϕ$, the $w_{ϕ, 0}$ value predicted from quintessential power-law cosmology is allowed within 1$σ$ uncertainty.

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