arXiv 1809.003412018-09gr-qc

$f(R)$引力场中两种不同形函数的可穿越虫洞和能量条件

Traversable Wormholes and Energy Conditions with Two Different Shape Functions in $f(R)$ Gravity

Nisha Godani, Gauranga C. Samanta

备注：: 25 pages, 80 figures, Accepted in IJMPD
DOI：: 10.1142/S0218271819500391

摘要：

由Morris \& Thorne \cite{morris1}提出的隧道结构--可穿越虫洞，在连接两个不同时空或同一时空的两个不同部分中具有重要作用。这些虫洞的特性取决于径向坐标下的红移和形状函数。文献中定义了几种形状函数，并研究了$f(R)$引力中关于这些形状函数\cite{lobo, saiedi, baha}的虫洞。本文考虑了两种形状函数（i）$b(r)=\dfrac{{r_0} \log (r+1)}{\log ({r_0}+1)}$和（ii）$b(r)=r_0(\frac{r}{r_0})^γ$，$0<γ<1$.第一个形状函数是新定义的，而第二个形状函数是从文献\cite{cataldo}中收集的。用$f(R)=R+αR^m-βR^{-n}$研究了$f(R)$引力中每种形状函数的虫孔，其中$m$，$n$，$α$和$β$为实常数.对不同参数的$α$或$β$、$f(R)$模型，对每种形状函数分五种情况进行了研究。在每种情况下，计算了能量密度、径向和切向压力、能量条件（包括零能量条件、弱能量条件、强能量条件和主导能量条件）以及各向异性参数。能量密度被发现是积极的，所有的能量条件得到违反支持虫洞的存在。此外，状态方程参数的值小于-1，这表明存在的幻影流体，并导致宇宙的膨胀。

英文摘要：

Traversable wormholes, tunnel like structures introduced by Morris \& Thorne \cite{morris1}, have a significant role in connection of two different space-times or two different parts of the same space-time. The characteristics of these wormholes depend upon the redshift and shape functions which are defined in terms of radial coordinate. In literature, several shape functions are defined and wormholes are studied in $f(R)$ gravity with respect to these shape functions \cite{lobo, saiedi, baha}. In this paper, two shape functions (i) $b(r)=\dfrac{{r_0} \log (r+1)}{\log ({r_0}+1)}$ and (ii) $b(r)=r_0(\frac{r}{r_0})^γ$, $0<γ<1$ are considered. The first shape function is newly defined, however the second one is collected from the literature\cite{cataldo}. The wormholes are investigated for each type of shape function in $f(R)$ gravity with $f(R)=R+αR^m-βR^{-n}$, where $m$, $n$, $α$, and $β$ are real constants. Varying parameters $α$ or $β$, $f(R)$ model is studied in five subcases for each type of shape function. In each case, the energy density, radial \& tangential pressures, energy conditions that include null energy condition, weak energy condition, strong energy condition \& dominated energy condition, and anisotropic parameter are computed. The energy density is found to be positive and all energy conditions are obtained to be violated which supports the existence of wormholes. Also, the equation of state parameter is obtained to possess values less than -1, that shows the presence of the phantom fluid and leads towards the expansion of the universe.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

摘要：

英文摘要：

相关论文