On the large-scale instability in interacting dark energy and dark matter fluids
On the large-scale instability in interacting dark energy and dark matter fluids
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DOI：
10.1103/physrevd.79.043526
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发表时间：
2009-01
影响因子：
5
通讯作者：
Brendan M. Jackson;A. Taylor;A. Berera
中科院分区：
文献类型：
--
作者：
Brendan M. Jackson;A. Taylor;A. Berera
[J]。Cosmol。Astropart。物理学博士[Phys. 07(2008) 020]报道了暗能量和暗物质耦合模型的大规模早期不稳定性。我们采用相同形式的能量-动量交换，并专门研究相互作用率仅与哈勃参数和暗能量密度成正比的情况。对于给定的状态参数方程，如果耦合足够小，则可以避免不稳定性。在超视界尺度下，导出了辐射和物质占主导的非绝热模态的表达式。我们还研究了在亚视界极限下暗物质扰动的增长。在那里我们发现，在暗能量开始占主导地位之前，耦合对结构的生长几乎没有影响。一旦宇宙开始加速，相对暗物质密度的波动不仅会像非耦合模型那样停止增长，而且实际上会随着宇宙的继续膨胀而衰减。
Recently, Valiviita et al. [J. Cosmol. Astropart. Phys. 07 (2008) 020] have reported a large-scale early-time instability in coupled dark energy and dark matter models. We take the same form of energy-momentum exchange and specialize to the case when the interaction rate is proportional to Hubble's parameter and the dark energy density only. Provided the coupling is made small enough for a given equation of state parameter, we show that the instability can be avoided. Expressions are derived for nonadiabatic modes on superhorizon scales in both the radiation and matter dominated regimes. We also examine the growth of dark matter perturbations in the subhorizon limit. There we find that the coupling has almost no effect upon the growth of structure before dark energy begins to dominate. Once the Universe begins to accelerate, the relative dark matter density fluctuations not only cease to grow as in uncoupled models, but actually decay as the Universe continues to expand.