The past lightcone of an observer in a cosmological spacetime is the unique geometric structure directly linked to observations. After general properties of the Hawking energy along slices of the past lightcone have previously been studied, the present work continues along this path by providing explicit cosmological applications of the Hawking energy associated with a lightcone. Firstly, it is shown that amongst all two-dimensional non-trapped spheres with equal area and average matter density, a shear-free matter distribution maximizes the Hawking energy for sufficiently high densities. Secondly, a Robertson–Walker reference slice is constructed for every lightcone slice based on area and energy. Thirdly, after a few pedagogical examples in concrete FLRW spacetimes, the implications of monotonicity of the energy down the lightcone are explored, arriving at two new bounds on the cosmic fluid’s density and equation-of-state parameter.

观察者在宇宙时空中的过去光锥是与观察直接相关的独特几何结构。在之前已经研究了沿过去光锥切片的霍金能量的一般特性之后，目前的工作通过提供与光锥相关的霍金能量的明确宇宙学应用沿着这条路径继续。首先，表明在所有具有相等面积和平均物质密度的二维非捕获球体中，无剪切物质分布使霍金能量最大化以达到足够高的密度。其次，根据面积和能量为每个光锥切片构建罗伯逊-沃克参考切片。第三，在具体 FLRW 时空中的一些教学示例之后，探索了光锥下能量单调性的含义，