关于振荡子的一点注记：预热期间不可忽略的度规涨落
A note on oscillons: non-negligible metric fluctuations during preheating
- Jagiellonian University（雅盖隆大学）
- University of Utah（犹他大学）
- Institute of Science Tokyo（东京科学大学）
- University of Portsmouth（朴茨茅斯大学）
- Universidade da Beira Interior（伊比利亚大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文指出预热期间度规涨落不可忽略，其贡献与暴胀场同阶，并修正格点模拟的Friedmann方程，建议用数值相对论处理非线性预热。
AI中文摘要：
后暴胀预热和振荡子形成的主流格点方法是在空间均匀的Friedmann-Lemaître-Robertson-Walker背景上演化非均匀暴胀场，其膨胀由体积平均能量密度驱动，而度规扰动被忽略。我们检验了这一近似与广义相对论的相容性。利用线性化爱因斯坦约束，我们表明慢滚暴胀特征性的Bardeen势抑制在预热期间消失：一旦第一个慢滚参数达到量级一，度规和暴胀场涨落便进入同一微扰阶。我们进一步表明，在固定FLRW方案中演化的标量场方程遗漏了由度规涨落产生的领头阶贡献。然后我们推导了ADM哈密顿约束的固有体积平均，并表明它并不归结为格点模拟中使用的Friedmann方程：精确的平均约束包含来自空间曲率、局部膨胀方差、剪切以及度规对局部能量密度修正的额外贡献。最后，我们针对Starobinsky和α-吸引子模型进行数值说明，在放大阶段度规贡献变得与标量场贡献相当。这些结果直接影响振荡子形成的标准格点描述，并促使数值相对论成为非线性预热问题的一致框架。
英文摘要：
The dominant lattice approach to post-inflationary preheating and oscillon formation evolves an inhomogeneous inflaton field on a spatially homogeneous Friedmann-Lemaître-Robertson-Walker background, whose expansion is sourced by a volume-averaged energy density, while metric perturbations are neglected. We examine the consistency of this approximation with General Relativity. Using the linearized Einstein constraints, we show that the suppression of the Bardeen potential, characteristic of slow-roll inflation, disappears during preheating: once the first slow-roll parameter becomes of order unity, the metric and inflaton fluctuations enter at the same perturbative order. We further show that the scalar-field equation evolved in the fixed-FLRW prescription omits leading-order contributions generated by metric fluctuations. We then derive the proper-volume average of the ADM Hamiltonian constraint and show that it does not reduce to the Friedmann equation used in lattice simulations: the exact averaged constraint contains additional contributions from the spatial curvature, the variance of the local expansion, the shear, and metric corrections to the local energy density. Finally, we illustrate numerically, for Starobinsky and $α$-attractor models, that the metric contribution becomes comparable to the scalar-field contribution during the amplification stage. These results directly affect the standard lattice description of oscillon formation and motivate numerical relativity as a consistent framework for the nonlinear preheating problem.
