The observed temperature fluctuations in the cosmic microwave background can be traced back to primordial curvature modes that are sourced by adiabatic and/or entropic matter perturbations. In this paper, we explore the entropic mechanism in the context of non-singular bouncing cosmologies. We show that curvature modes are naturally generated during `graceful exit,' i.e., when the smoothing slow contraction phase ends and the universe enters the bounce stage. Here, the key role is played by the kinetic energy components that come to dominate the energy density and drive the evolution towards the cosmological bounce.

中文翻译：

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非奇异弹跳宇宙学中具有熵扰动的源曲率模式

在宇宙微波背景中观察到的温度波动可以追溯到由绝热和/或熵物质扰动引起的原始曲率模式。在本文中，我们探索了非奇异弹跳宇宙学背景下的熵机制。我们表明曲率模式是在“优雅退出”期间自然产生的，即当平滑缓慢收缩阶段结束并且宇宙进入反弹阶段时。在这里，起关键作用的是动能分量，这些动能分量开始主导能量密度并推动宇宙学反弹的演化。