Stochastic inflation in phase space: is slow roll a stochastic attractor?
Stochastic inflation in phase space: is slow roll a stochastic attractor?
复制标题
相空间中的随机膨胀：慢滚是随机吸引子吗？
DOI：
10.1088/1475-7516/2017/05/045
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发表时间：
2017
影响因子：
6.4
通讯作者：
V. Vennin
中科院分区：
文献类型：
--
作者：
J. Grain;V. Vennin
暴胀宇宙学的一个吸引人的特征是相空间吸引子的存在，“慢滚”，它消除了对初始场速度的依赖。利用相空间方法中的随机暴胀形式研究了该性质在量子涨落反作用下的鲁棒性。提出了随机膨胀的哈密顿公式，其中表明粗粒化过程-波长小于哈勃半径的积分-保留了自由场的规范结构。这意味着不同的规范变量集产生相同的概率分布，这澄清了关于这个问题的文献。还分析了量子到经典跃迁所起的作用，并表明它约束了粗粒化尺度。在自由场的情况下，我们发现量子扩散在相空间中与慢滚方向对齐。这意味着经典慢滚吸引子不受随机效应的影响，因此可以推广为随机吸引子，无论初始条件如何，其松弛时间至少与经典系统一样短。然而，对于非测试场或具有非线性自相互作用的测试场，量子扩散与经典慢滚流是不一致的。我们在粗粒度尺度上推导了一个条件，使得在慢滚动的领先阶上，这种偏差的观测修正可以忽略不计。
An appealing feature of inflationary cosmology is the presence of a phase-space attractor, ``slow roll'', which washes out the dependence on initial field velocities. We investigate the robustness of this property under backreaction from quantum fluctuations using the stochastic inflation formalism in the phase-space approach. A Hamiltonian formulation of stochastic inflation is presented, where it is shown that the coarse-graining procedure—where wavelengths smaller than the Hubble radius are integrated out—preserves the canonical structure of free fields. This means that different sets of canonical variables give rise to the same probability distribution which clarifies the literature with respect to this issue. The role played by the quantum-to-classical transition is also analysed and is shown to constrain the coarse-graining scale. In the case of free fields, we find that quantum diffusion is aligned in phase space with the slow-roll direction. This implies that the classical slow-roll attractor is immune to stochastic effects and thus generalises to a stochastic attractor regardless of initial conditions, with a relaxation time at least as short as in the classical system. For non-test fields or for test fields with non-linear self interactions however, quantum diffusion and the classical slow-roll flow are misaligned. We derive a condition on the coarse-graining scale so that observational corrections from this misalignment are negligible at leading order in slow roll.
随机旁观者
影响因子：
6.4
作者：
Hardwick R
通讯作者：
Hardwick R
影响因子：
5.4
作者：
Burgess, C. P.;Holman, R.;Williams, M.
通讯作者：
Williams, M.