Abstract
Multiple modifications of general relativity (GR) have been proposed in the literature in order to understand the nature of the accelerated expansion of the Universe. However, thus far all the predictions of GR have been confirmed with constantly increasing accuracy. In this work, we study the imprints of a particular class of models – “screened” modified gravity theories – on cosmic filaments. We have utilized the N-body code ISIS/RAMSES to simulate the symmetron model and the Hu–Sawicky f(R) model, and we post-process the output with DisPerSE to identify the filaments of the cosmic web. We investigated how the global properties of the filaments – such as their lengths, masses, and thicknesses – as well as their radial density and speed profiles change under different gravity theories. We find that filaments are, on average, shorter and denser in modified gravity models compared to in ΛCDM. We also find that the speed profiles of the filaments are enhanced, consistent with theoretical expectations. Overall, our results suggest that cosmic filaments can be an effective complementary probe of screened modified gravity theories on Mpc scales.
Highlights
The current standard model of cosmology is ΛCDM
We examine the filament properties and their radial density and speed profiles in Sect. 4, and we investigate how these differ in modified gravity compared to ΛCDM
We present the distributions of filament length, mass, and thickness in ΛCDM and modified gravity simulations, as well as the correlations between these properties
Summary
The current standard model of cosmology is ΛCDM. By introducing two major unknowns in the theory, cold dark matter (CDM) and a cosmological constant (Λ), this model provides an excellent fit to many observations on large scales, such as the cosmic microwave background (Melchiorri et al 2000; Netterfield et al 2002; Bennett et al 2013; Planck Collaboration XIII 2016) and the late-time acceleration of the Universe as measured from Type Ia supernovae (Riess et al 1998; Perlmutter et al 1999; Tonry et al 2003). Gravitational tests on Earth and within the Solar System, constrain the strength of a potential fifth force to be orders of magnitude lower than its Newtonian counterpart (for a review of local constraints see Will 2006). This implies that if a scalar field coupled to matter exists in the Universe, the fifth force must be somehow suppressed in certain environments to satisfy the current constraints. There are many such screening mechanisms that hide the fifth force in high-density regions (see, e.g., Khoury 2010; Joyce et al 2015, for reviews)
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