论文标题
早期宇宙重力产生的衍生耦合
Derivative couplings in gravitational production in the early universe
论文作者
论文摘要
早期宇宙中的重力颗粒产生是由于物质场与曲率的耦合所致。该耦合可能包括修改动力学项的衍生术语。最通用的一阶动作包含曲率标量和无可纹理量张量的衍生耦合，在（伪）NAMBU-GOLDSTONE玻色子或异形标量（例如Branons）的情况下，它们可能占主导地位。在存在这些衍生耦合的情况下，在DE Sitter阶段（模拟膨胀）在DE Sitter阶段产生的颗粒的密度是恒定的，并且会随着有效的质量而衰减（这又取决于耦合到曲率标量的耦合）。在通货膨胀后的再加热阶段，背景曲率的衍生耦合的存在也会以非平凡的方式改变重力产生，即使在扰动状态下也是如此。我们还表明，两个耦合 - 到曲率标量和无可纹理的ricci张量 - 尤其是大质量的耦合。在这种制度中，生产对以前的耦合变得高度敏感，而它变得独立于后者。
Gravitational particle production in the early universe is due to the coupling of matter fields to curvature. This coupling may include derivative terms that modify the kinetic term. The most general first order action contains derivative couplings to the curvature scalar and to the traceless Ricci tensor, which can be dominant in the case of (pseudo-)Nambu-Goldstone bosons or disformal scalars, such as branons. In the presence of these derivative couplings, the density of produced particles for the adiabatic regime in the de Sitter phase (which mimics inflation) is constant in time and decays with the inverse effective mass (which in turn depends on the coupling to the curvature scalar). In the reheating phase following inflation, the presence of derivative couplings to the background curvature modifies in a nontrivial way the gravitational production even in the perturbative regime. We also show that the two couplings -- to the curvature scalar and to the traceless Ricci tensor -- are drastically different, specially for large masses. In this regime, the production becomes highly sensitive to the former coupling while it becomes independent of the latter.
