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تسجيل مستخدم جديدHow to Build a Catalogue of Linearly-Evolving Cosmic Voids
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Cosmic voids provide a powerful probe of the origin and evolution of structures in the Universe because their dynamics can remain near-linear to the present day. As a result they have the potential to connect large scale structure at late times to early-Universe physics. Existing watershed-based algorithms, however, define voids in terms of their morphological properties at low redshift. The degree to which the resulting regions exhibit linear dynamics is consequently uncertain, and there is no direct connection to their evolution from the initial density field. A recent void definition addresses these issues by considering anti-halos. This approach consists of inverting the initial conditions of an $N$-body simulation to swap overdensities and underdensities. After evolving the pair of initial conditions, anti-halos are defined by the particles within the inverted simulation that are inside halos in the original (uninverted) simulation. In this work, we quantify the degree of non-linearity of both anti-halos and watershed voids using the Zeldovich approximation. We find that non-linearities are introduced by voids with radii less than $5,mathrm{Mpc},h^{-1}$, and that both anti-halos and watershed voids can be made into highly linear sets by removing these voids.
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We showed how the shape of cosmic voids can be used to distinguish between different models of dark energy using galaxy positions.
Cosmic voids, the less dense patches of the Universe, are promising laboratories to extract cosmological information. Thanks to their unique low density character, voids are extremely sensitive to diffuse components such as neutrinos and dark energy,
and represent ideal environments to study modifications of gravity, where the effects of such modifications are expected to be more prominent. Robust void-related observables, including for example redshift-space distortions (RSD) and weak lensing around voids, are a promising way to chase and test new physics. Cosmological analysis of the large-scale structure of the Universe predominantly relies on the high density regions. Current and upcoming surveys are designed to optimize the extraction of cosmological information from these zones, but leave voids under-exploited. A dense, large area spectroscopic survey with imaging capabilities is ideal to exploit the power of voids fully. Besides helping illuminate the nature of dark energy, modified gravity, and neutrinos, this survey will give access to a detailed map of under-dense regions, providing an unprecedented opportunity to observe and study a so far under-explored galaxy population.
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