跃迁红移：来自参数和非参数方法的新约束
Transition Redshift: New constraints from parametric and nonparametric methods
摘要：
在本文中，我们使用宇宙运动学方法来研究宇宙的加速膨胀。这是一个独立于模型的方法，只依赖于宇宙是均匀和各向同性的假设，并由FRW度规描述。我们参数化的减速参数，$q(z)$，以限制过渡红移（$z_t$）在宇宙膨胀从减速到加速阶段。我们使用三种不同的参数化$q(z)$，即，$q_\I(z)=q_{\textnormal{\tiny\textsc{1}}}+q_{\textnormal{\tiny\textsc{2}}}z$，$q_\II (z) = q_\3 + q_\4 \ln (1 + z)$和$q_\III(z)=\frac{1}{2}+\frac{q_{\textnormal{\tiny\textsc{5}}}}{(1+z)^2}$。对星系年龄、强透镜效应和Ia超新星数据的联合分析表明，跃迁红移小于1，即$z_t<1$。我们还使用非参数方法（LOESS+SIMEX）来约束$z_t$。这也给出了与通过参数方法获得的值一致的$z_t<1$。
英文摘要：
In this paper, we use the Cosmokinematics approach to study the accelerated expansion of the Universe. This is a model independent approach and depends only on the assumption that the Universe is homogeneous and isotropic and is described by the FRW metric. We parametrize the deceleration parameter, $q(z)$, to constrain the transition redshift ($z_t$) at which the expansion of the Universe goes from a decelerating to an accelerating phase. We use three different parametrizations of $q(z)$ namely, $q_\I(z)=q_{\textnormal{\tiny\textsc{1}}}+q_{\textnormal{\tiny\textsc{2}}}z$, $q_\II (z) = q_\3 + q_\4 \ln (1 + z)$ and $q_\III(z)=\frac{1}{2}+\frac{q_{\textnormal{\tiny\textsc{5}}}}{(1+z)^2}$. A joint analysis of the age of galaxies, strong lensing and supernovae Ia data indicates that the transition redshift is less than unity i.e. $z_t<1$. We also use a nonparametric approach (LOESS+SIMEX) to constrain $z_t$. This too gives $z_t<1$ which is consistent with the value obtained by the parametric approach.
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