Time scales for nonlinear processes in preheating after multifield inflation with nonminimal couplings
Time scales for nonlinear processes in preheating after multifield inflation with nonminimal couplings
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DOI：
10.1103/physrevd.102.043528
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发表时间：
2020-05
影响因子：
5
通讯作者：
Jorinde van de Vis;Rachel Nguyen;E. Sfakianakis;J. Giblin;D. Kaiser
中科院分区：
文献类型：
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作者：
Jorinde van de Vis;Rachel Nguyen;E. Sfakianakis;J. Giblin;D. Kaiser
我们进行了广泛的格子模拟来研究包含非最小耦合的多场模型的后膨胀动力学。我们探讨了这些模型中预热的参数依赖关系，并描述了控制能量转移、再散射以及辐射控制和热化等非线性过程的各种时间尺度。在大的非最小耦合极限($xi_i\sim 100$)中，我们发现能量从膨胀凝聚到辐射自由度的有效转移、辐射主导的物态方程的出现和热化的开始都在膨胀结束后的$N_(Rm)reh}\s$e的范围内一致地发生，基本上与模型中其他耦合的值无关。负椭圆度是个例外，在这种情况下，系统演化所沿场空间的主要方向与较大的非最小耦合数之间存在不对准。在这些情况下，场空间驱动的参数共振被有效地关闭。更广泛地说，标量场的势和场-空间流形结构之间的竞争可能会产生有趣的现象，如两级共振。尽管爆炸粒子的产生可能导致背景能量密度的迅速耗尽，但在这些模型中，在暴涨结束后，非线性过程不会引起任何超视界关联，这使得对CMB观测的预测不受等温涨落后期放大的影响。因此，即使当我们考虑通胀后的动态时，这类模型也保留了原始可观测数据和最近观测数据之间的极好一致性。
We have conducted extensive lattice simulations to study the post-inflation dynamics of multifield models involving nonminimal couplings. We explore the parameter dependence of preheating in these models and describe the various time-scales that control such nonlinear processes as energy transfer, re-scattering, and the approach to radiation-domination and thermalization. In the limit of large nonminimal couplings ($\xi_I \sim 100$), we find that efficient transfer of energy from the inflaton condensate to radiative degrees of freedom, emergence of a radiation-dominated equation of state, and the onset of thermalization each consistently occur within $N_{\rm reh} \lesssim 3$ $e$-folds after the end of inflation, largely independent of the values of the other couplings in the models. The exception is the case of negative ellipticity, in which there is a misalignment between the dominant direction in field-space along which the system evolves and the larger of the nonminimal couplings $\xi_I$. In those cases, the field-space-driven parametric resonance is effectively shut off. More generally, the competition between the scalar fields' potential and the field-space manifold structure can yield interesting phenomena such as two-stage resonances. Despite the explosive particle production, which can lead to a quick depletion of the background energy density, the nonlinear processes do not induce any super-horizon correlations after the end of inflation in these models, which keeps predictions for CMB observables unaffected by the late-time amplification of isocurvature fluctuations. Hence the excellent agreement between primordial observables and recent observations is preserved for this class of models, even when we consider post-inflation dynamics.