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Determining the Equation of State of the Expanding Universe: Inverse Problem in Cosmology

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arxiv astro-ph/9810447 v3 pith:QA5XPVHV submitted 1998-10-28 astro-ph hep-ph

Takashi Nakamura , Takeshi Chiba This is my paper · ORCID
classification astro-phhep-ph
keywords universeequationstatedeterminedexamplemightparameterredshift
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abstract

Even if the luminosity distance as a function of redshift is obtained accurately using, for example, Type Ia supernovae, the equation of state of the Universe cannot be determined uniquely but depends on one free parameter $\Omega_{k0} ={k}/(a_0^2H_0^2)$, where $a_0$ and $H_0$ are the present scale factor and the Hubble parameter, respectively. This degeneracy might be resolved if, for example, the time variations of the redshift of quasars are measured as proposed recently by Loeb. Therefore the equation of state of the Universe (or the metric of the universe) might be determined without any theoretical assumption on the matter content of the Universe in future.

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Cited by 3 Pith papers

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    hep-th 2025-02 conditional novelty 5.0 of 10

    A sextic ghost condensate dark energy model is shown to produce a matter-density-dependent correction to the Newtonian potential and a frequency-dependent gravitational wave speed in de Sitter spacetime.

  3. EFT of Dark Energy with Cosmic Chronometers: Reconstructing Background EFT Functions

    astro-ph.CO 2025-12 unverdicted novelty 4.0 of 10

    Reconstruction of EFT background functions from cosmic chronometer Hubble data allows model-independent tests of dark energy evolution in scalar-tensor theories.

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