Coupled dark energy: towards a general description of the dynamics
Coupled dark energy: towards a general description of the dynamics
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DOI：
10.1088/1475-7516/2005/06/007
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发表时间：
2005-02
影响因子：
6.4
通讯作者：
Burin Gumjudpai;T. Naskar;M. Sami;S. Tsujikawa
中科院分区：
文献类型：
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作者：
Burin Gumjudpai;T. Naskar;M. Sami;S. Tsujikawa
在标量场与正压理想流体耦合的暗能量模型中，宇宙标度解的存在将场φ的拉格朗日量限制为p = Xg（λφ），其中λ为常数，g为任意函数。我们推导出一般的演化方程在一个自治的形式，这个拉格朗日和调查几个不同的暗能量模型的不动点的稳定性：（i）普通（幻影）领域，（ii）电子幽灵凝聚，（iii）（幻影）快子。我们发现在所有的模型中，无论暗能量和暗物质之间是否存在耦合Q，都存在加速膨胀的标量场主导不动点（Ωφ = 1）。这些不动点对于幻影场来说总是经典稳定的，这意味着如果幻影场是暗能量的来源，那么宇宙最终会被标量场的能量密度所控制。当场φ的状态方程wφ大于−1时，我们发现如果标量场主导解不稳定，则标度解是稳定的，反之亦然。因此，在这种情况下，最终吸引子要么是常数Ωφ满足0 < Ωφ < 1的标度解，要么是Ωφ = 1的标量场主导解。
In dark energy models of scalar-field coupled to a barotropic perfect fluid, the existence of cosmological scaling solutions restricts the Lagrangian of the field φ to p = Xg(Xeλφ), where , λ is a constant and g is an arbitrary function. We derive general evolution equations in an autonomous form for this Lagrangian and investigate the stability of fixed points for several different dark energy models: (i) ordinary (phantom) field, (ii) dilatonic ghost condensate, and (iii) (phantom) tachyon. We find the existence of scalar-field dominant fixed points (Ωφ = 1) with an accelerated expansion in all models irrespective of the presence of the coupling Q between dark energy and dark matter. These fixed points are always classically stable for a phantom field, implying that the universe is eventually dominated by the energy density of a scalar field if a phantom is responsible for dark energy. When the equation of state wφ for the field φ is larger than −1, we find that scaling solutions are stable if the scalar-field dominant solution is unstable, and vice versa. Therefore in this case the final attractor is either a scaling solution with constant Ωφ satisfying 0 < Ωφ < 1 or a scalar-field dominant solution with Ωφ = 1.