论文标题

宇宙的大规模几何形状

Large-scale geometry of the Universe

论文作者

Awwad, Yassir, Prokopec, Tomislav

论文摘要

后期宇宙的大规模几何形状可以分解为r $ \ timesσ_3$,其中r代表宇宙时间,$σ_3$是三维空间歧管。我们推测,宇宙空间部分的空间几何形状$σ_3$符合Thurston-Perelman定理,根据该定理,$σ_3$的几何形状是瑟斯顿几何化的八个几何形状之一,或者是Thurston Geimetrization Issureture的八个几何形状之一,或者是Thurston Geometries Clookally seclys seemerties seplys seementies。我们假设单个几何形状的拓扑没有发挥观察作用,即单个几何形状的大小比当今的哈勃半径大得多。我们通过使用简化的假设,即我们的本地哈勃贴片仅由一个几何形状组成,这在非常大的尺度上大致均匀,但是通常违反了空间各向同性,我们研究了每个单个几何形状的动力学。空间各向异性在减速的宇宙中随时间增长,但它们会在加速宇宙中衰减。这样创建的各向异性问题可以通过原始通货膨胀的时期解决,类似于如何解决平坦性问题。因此,关于宇宙的大规模几何形状,瑟斯顿的几何形状都应与弗里德曼的几何形状相提并论。我们考虑了两种可用于测试我们猜想的观察方法:一种基于光度距离,一种基于角直径距离测量值,但留给未来的预测实现。

The large scale geometry of the late Universe can be decomposed as R$\times Σ_3$, where R stands for cosmic time and $Σ_3$ is the three dimensional spatial manifold. We conjecture that the spatial geometry of the Universe's spatial section $Σ_3$ conforms with the Thurston-Perelman theorem, according to which the geometry of $Σ_3$ is either one of the eight geometries from the Thurston geometrization conjecture, or a combination of Thurston geometries smoothly sewn together. We assume that topology of individual geometries plays no observational role, i.e. the size of individual geometries is much larger than the Hubble radius today. We investigate the dynamics of each of the individual geometries by making use of the simplifying assumption that our local Hubble patch consists of only one such geometry, which is approximately homogeneous on very large scales, but spatial isotropy is generally violated. Spatial anisotropies grow in time in decelerating universes, but they decay in accelerating universes. The thus-created anisotropy problem can be solved by a period of primordial inflation, akin to how the flatness problem is solved. Therefore, as regards Universe's large scale geometry, any of the Thurston's geometries should be considered on a par with Friedmann's geometries. We consider two observational methods that can be used to test our conjecture: one based on luminosity distance and one on angular diameter distance measurements, but leave for the future their detailed forecasting implementations.

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