Challenges to Self-Acceleration in Modified Gravity from Gravitational Waves and Large-Scale Structure

By L. Lombriser, N. A. Lima. 2016

242 citations recorded by the source corpus.

Abstract With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 observations, a measurement of the cosmological speed of gravity will likely soon be realised. We show that a confirmation of equality to the speed of light as indicated by indirect Galactic observations will have important consequences for a very large class of alternative explanations of the late-time accelerated expansion of our Universe. It will break the dark degeneracy of self-accelerated Horndeski scalar–tensor theories in the large-scale structure that currently limits a rigorous discrimination between acceleration from modified gravity and from a cosmological constant or dark energy. Signatures of a self-acceleration must then manifest in the linear, unscreened cosmological structure. We describe the minimal modification required for self-acceleration with standard gravitational-wave speed and show that its maximum likelihood yields a 3σ poorer fit to cosmological observations compared to a cosmological constant. Hence, equality between the speeds challenges the concept of cosmic acceleration from a genuine scalar–tensor modification of gravity.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/46eece6cefc58febf0016ec3d60cf3fd294d1835

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Citations in the corpus

Gravitation (2019, background): “However, most of these models predict that gravitational and electromagnetic waves have different propagation speed [31], which is now excluded.”
Horndeski theory and beyond: a review (2019, background): “Measuring the speed of gravitational waves cGW can be a test for modified gravity theories [176, 177, 178].”
Dark Energy in Light of Multi-Messenger Gravitational-Wave Astronomy (2018, unknown): “, 2016) and models with self-acceleration (Lombriser and Taylor, 2016; Lombriser and Lima, 2017).”
Probing the theory of gravity with gravitational lensing of gravitational waves and galaxy surveys (2019, background): “(9) (Carroll et al. 2006; Bean et al. 2007; Hu & Sawicki 2007; Schmidt 2008; Silvestri et al. 2013; Baker et al. 2015; Lombriser & Taylor 2016; Lombriser & Lima 2017; Saltas et al. 2014; Baker & Bull 2015; Slosar et al. 2019) such as (i) g(k, z) 6= 0, (ii) the modified Poisson Equation, (iii)…”
Testing modified gravity at cosmological distances with LISA standard sirens (2019, background): “Minimal self-acceleration λ ( ln aacc + C 2 χacc ) C/H0−2 ln a(2)acc−Cχacc [66]”
Effective field theory of dark energy: A review (2019, background): “Note that when imposing c(2)t = 1, these models produce a 3σ poorer fit to cosmological observables as compared to ΛCDM [241], challenging the concept of self-acceleration within Horndeski theories.”
A systematic approach to generalisations of General Relativity and their cosmological implications (2018, background): “If we decide to be too conservative and ignore the presence of the higher order operators, that would enter naturally from the effective field theory point of view, we can then put very restrictive bounds on the modified gravity theories [275, 276, 277, 278, 279, 280, 281, 282].”