在具有$Λ(T)$的$f(R,T)$引力中的Bianchi型- $V$宇宙学
Bianchi Type-$V$ cosmology in $f(R,T)$ gravity with $Λ(T)$
摘要：
研究了Harko等人（2011）提出的$f(R, T)$修正引力理论中的一类新的宇宙学模型，其中引力拉格朗日量由Ricci标量$R$的任意函数和应力-能量张量$T$的迹给出，通过考虑时间相关的减速参数，选择特定的$f(R, T) = f_{1}(R) + f_{2}(T)$.时间相关减速参数（DP）的概念与一些适当的假设产生的平均比例因子$a(t) = \sinh^{\frac{1}{n}}(αt)$，其中$n$和$α$是正常数。对于$0 < n \leq 1$，这产生了一类加速模型，而对于$n > 1$，宇宙模型表现出从早期减速相到现在加速相的相变，这与最近的天体物理观测结果是一致的。我们的目的是重建$f(R,T)$模型的启发，这个特殊的法律与修改的引力理论的减速参数。在本研究中，我们考虑宇宙学常数$Λ$作为应力能量-动量-张量的迹的函数，并称这样的模型为“$Λ(T)$引力”，其中我们指定了一定形式的$Λ(T)$。这样的模型可能显示出与宇宙学观测更好的一致性。状态探测器诊断对$\{r,s\}$参数已被用来表征宇宙的不同阶段。我们还讨论了衍生模型的物理后果。
英文摘要：
A new class of cosmological models in $f(R, T)$ modified theories of gravity proposed by Harko et al. (2011), where the gravitational Lagrangian is given by an arbitrary function of Ricci scalar $R$ and the trace of the stress-energy tensor $T$, have been investigated for a specific choice of $f(R, T) = f_{1}(R) + f_{2}(T)$ by considering time dependent deceleration parameter. The concept of time dependent deceleration parameter (DP) with some proper assumptions yield the average scale factor $a(t) = \sinh^{\frac{1}{n}}(αt)$, where $n$ and $α$ are positive constants. For $0 < n \leq 1$, this generates a class of accelerating models while for $n > 1$, the models of universe exhibit phase transition from early decelerating phase to present accelerating phase which is in good agreement with the results from recent astrophysical observations. Our intention is to reconstruct $f(R,T)$ models inspired by this special law for the deceleration parameter in connection with the theories of modified gravity. In the present study we consider the cosmological constant $Λ$ as a function of the trace of the stress energy-momentum-tensor, and dub such a model "$Λ(T)$ gravity" where we have specified a certain form of $Λ(T)$. Such models may display better uniformity with the cosmological observations. The statefinder diagnostic pair $\{r,s\}$ parameter has been embraced to characterize different phases of the universe. We also discuss the physical consequences of the derived models.
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