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arXiv 1002.2042astro-ph.COgr-qchep-phhep-th
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标量张量宇宙学中暗能量微扰的演化

Evolution of Dark Energy Perturbations in Scalar-Tensor Cosmologies

J. C. Bueno Sanchez, L. Perivolaropoulos

摘要:

我们通过解析和数值求解标量张量宇宙学中的广义爱因斯坦方程,得到了暗能量和物质线性微扰的演化。我们比较我们的结果与相应的结果最小耦合quintessence扰动。我们的结果自然(O(1))值的拉格朗日参数,导致类似于LCDM的背景展开总结如下:1。在小于100 h^{-1} Mpc的尺度上,标量-张量暗能量密度扰动与最小耦合的精粹扰动相比,被放大了约10^6倍。在这些尺度上,暗能量扰动与物质密度扰动相比只占10%左右。2.标量张量暗能量密度扰动与亚哈勃尺度上的物质线性扰动反相关。因此,星系团被预测与暗能量的空洞重叠。3.这种物质与负压扰动的反相关性导致了物质扰动在亚哈勃尺度上轻微放大约10%。4.亚哈勃尺度上标量场扰动的演化与尺度无关,因此它对应于消失的有效声速(c_{sΦ} =0)。它还涉及由场的放大有效质量引起的早期大振荡。这种放大是由于场与里奇曲率标量以及(因此)与物质的非最小耦合。没有这样的振荡存在于最低限度的耦合的精粹扰动,这是抑制亚哈勃尺度(c_{sΦ} =1)。我们的研究结果的影响,包括修改后的预测集群晕配置文件观察到的属性。已知这些剖面与LCDM的预测存在一定的张力。

英文摘要:

We solve analytically and numerically the generalized Einstein equations in scalar-tensor cosmologies to obtain the evolution of dark energy and matter linear perturbations. We compare our results with the corresponding results for minimally coupled quintessence perturbations. Our results for natural (O(1)) values of parameters in the Lagrangian which lead to a background expansion similar to LCDM are summarized as follows: 1. Scalar-Tensor dark energy density perturbations are amplified by a factor of about 10^6 compared to minimally coupled quintessence perturbations on scales less than about 100 h^{-1} Mpc. On these scales dark energy perturbations constitute a fraction of about 10% compared to matter density perturbations. 2. Scalar-Tensor dark energy density perturbations are anti-correlated with matter linear perturbations on sub-Hubble scales. Thus clusters of galaxies are predicted to overlap with voids of dark energy. 3. This anti-correlation of matter with negative pressure perturbations induces a mild amplification of matter perturbations by about 10% on sub-Hubble scales. 4. The evolution of scalar field perturbations on sub-Hubble scales, is scale independent and therefore it corresponds to a vanishing effective speed of sound (c_{sΦ}=0). It also involves large oscillations at early times induced by the amplified effective mass of the field. This amplification is due to the non-minimal coupling of the field to the Ricci curvature scalar and (thus) to matter. No such oscillations are present in minimally coupled quintessence perturbations which are suppressed on sub-Hubble scales (c_{sΦ}=1). Implications of our results include modified predictions for cluster halo profiles observed properties. These profiles are known to be in some tension with the predictions of LCDM.

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