Measuring the equation of state of the universe: Pitfalls and prospects

By Irit Maor, R. Brustein, J. McMahon, Paul J. Steinhardt. 2001

151 citations recorded by the source corpus.

We explore various pitfalls and challenges in determining the equation of state $(w)$ of the dark energy component that dominates the universe and causes the current accelerated expansion. We demonstrated in an earlier paper the existence of a degeneracy that makes it impossible to resolve well the value of w or its time derivative with supernovae data. Here we consider standard practices, such as assuming that w is constant or greater than $\ensuremath{-}1,$ and show that they also can lead to gross errors in estimating the true equation of state. We further consider combining measurements of the cosmic microwave background anisotropy and the Alcock-Paczynski test with supernovae data and find that the improvement in resolving the time derivative of w is marginal, although the combination can constrain its present value perhaps to 20% uncertainty.

Subfields: Astronomy and Astrophysics, Oceanography

View Paper: https://www.semanticscholar.org/paper/44c5d5546c0f74ec479191a0aafe27ce874d2a6b

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Citations in the corpus

The Cosmological Constant and Dark Energy (2002, background): “This is clearly illustrated by Maor et al. (2002).”
Large‐scale cosmic microwave background anisotropies and dark energy (2003, background): “Finally, we found as a posterior mean value for the equation of state parameter w = −1.02, although this conclusion might depend to some extent on our choice of a constant equation of state parametrization (Maor et al. 2002).”
Exploring the expanding Universe and dark energy using the statefinder diagnostic (2003, background): “Yet another approach (Maor et al. 2002) advocated a quadratic fit to the total equation of state: wT (z) = w0 + w1z +w2z 2 , (44) where the total equation of state, wT (z), is defined in terms of the equation of state of dark energy, w(z), as wT (z) = w(z) 1 + Ωm 1−Ωm exp [ −3 ∫ 1+z 1 w(x) dx x ] .”
The Essence of Quintessence and the Cost of Compression (2004, background): “The most basic parametrisation, namely describing the dark energy with a constant equation of state w = w0, is well-known to introduce a severe bias (see for instance Maor et al. 2002, Virey et al. 2004) in parameter estimation.”
Smoothing supernova data to reconstruct the expansion history of the universe (2005, background): “…et al. 2003; Alam et al. 2004; Alam, Sahni & Starobinsky 2004 a), w(z) (Chevallier & Polarski 2001; Weller & Albrecht 2002; Gerke & Efstathiou 2002; Maor et al. 2002; Corasaniti & Copeland 2003; Linder 2003; Wang & Mukherjee 2004; Saini, Weller & Bridle 2004; Nesseris & Perivelaroupolos 2004; Gong…”
Cosmological parameters from supernova observations: A critical comparison of three data sets (2003, unknown): “…2001; Leibundgut 2001; Trentham 2001; Podariu, Nugent, & Ratra 2001; Corasaniti & Copeland 2002; Kujat et al. 2002; Minty, Heavens, & Hawkins 2002; Maor et al. 2002; Weller & Albrecht 2002; Gerke & Efstathiou 2002; Rowan-Robinson 2002; Linder & Jenkins 2003; Padmanabhan & Choudhury 2003; Visser…”