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The Mirage of w=-1

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arxiv 0708.0024 v1 pith:WRNTDB6X submitted 2007-08-01 astro-ph

The Mirage of w=-1

classification astro-ph
keywords constantcosmologicalredshiftdarkenergyequationhighstate
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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We demonstrate that cosmic microwave background observations consistent with a cosmological constant universe predict in a well-defined sense that lower redshift measures will nearly automatically deliver w=-1 for the dark energy equation of state value unless they are sensitive to w(z). Thus low redshift data pointing to w=-1 does not truly argue for a cosmological constant. Even the simplest question of whether the equation of state of dark energy is equal to the cosmological constant therefore requires experiments able to sensitively constrain time variation w(z) and not merely a constant w. We also note a number of issues regarding parametrization of w(z), demonstrating that the standard form w(z)=w_0+w_a z/(1+z) is robust but use of high order polynomials and cutting off the high redshift behavior can be pathological.

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Cited by 7 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

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