Cosmology with x matter
Cosmology with x matter
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DOI：
10.1093/mnras/289.2.l5
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发表时间：
1997-04
影响因子：
4.8
通讯作者：
T. Chiba;N. Sugiyama;Takashi Nakamura
中科院分区：
文献类型：
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作者：
T. Chiba;N. Sugiyama;Takashi Nakamura
受H_0t_0和t_0分别为哈勃参数和宇宙年龄的可能性的启发，我们研究了包括x物质在内的宇宙学。X物质用状态方程$p_x=w0\rho_{x0}+c_S^2(rho_x-rho_{x0})$表示，其中$p_x$、$rho_x$和$rho_(x0})分别是x物质的压强、密度和密度。$w_0$和$c_S^2$一般是$\rho_x$的函数。X物质具有状态方程的最一般形式，它的特征是：1)破坏了目前强能条件下的$w0<；-1/3$；2)局部稳定的(即$c_S^2\geq0$)；3)保证因果关系($c_S\leq1$)。考虑到$w_0$和$c_S^2$是常数的情况，我们发现在$(w_0，c_S^2，欧米茄{x0})$的大参数空间中，模型宇宙与宇宙的年龄和遥远的I型超新星的观测是一致的。
Motivated by the possibility of $H_0t_0 > 1$ where $H_0$ and $t_0$ are the Hubble parameter and the age of the universe, respectively, we investigate the cosmology including x-matter. x-matter is expressed by the equation of state $p_x=w_0\rho_{x0} + c_s^2(\rho_x-\rho_{x0})$, where $p_x$, $\rho_x$ and $\rho_{x0}$ are the pressure, the density of x-matter and the density at present, respectively. $w_0$ and $c_s^2$ are functions of $\rho_x$ in general. x-matter has the most general form of the equation of state which is characterized by 1)violation of strong energy condition at present for $w_0 < -1/3$ ; 2) locally stable (i.e. $c_s^2\geq 0$); 3)causality is guaranteed ($c_s\leq 1$). Considering the case that $w_0$ and $c_s^2$ are constants, we find that there is a large parameter space of $(w_0,c_s^2,\Omega_{x0})$ in which the model universe is consistent with the age of the universe and the observations of distant Type I supernovae.