2009/02/28 by Ishwaree P. Neupane, ISHWAREE P. NEUPANE, Holly Trowland +1 · 1 citation
Physics and Astronomy · #Ansatz #Cosmological constant #Cosmology and Gravitation Theories #Dark energy #Dark fluid #Dark matter #Dilaton #Galaxies: Formation, Evolution, Phenomena #Lambda-CDM model #Particle physics theoretical and experimental studies #Quintessence #Scalar field #astro-ph.CO #gr-qc #hep-ph #hep-th
paper · pdf · doi:10.1142/s0218271810016415
published as Int.J.Mod.Phys.D19:367-394,2010 · 32 pages, several eps figures; refs added, matches published version
openalex publication_date 2010/03/01 · arxiv created 2010/03/10 · arxiv updated 2010/04/28 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Dark energy is some of the weirdest and most mysterious stuff in the universe that tends to increase the rate of expansion of the universe. Two commonly known forms of dark energy are the cosmological constant, a constant energy density filling space homogeneously, and scalar fields such as quintessence or moduli whose energy density can vary with time. We explore one particular model for dynamic dark energy: quintessence driven by a scalar dilaton field. We propose an ansatz for the form of the dilaton field, |ϕ(a)|m P ≡ α 1 ln t + α 2 t n = α ln a + βa 2ζ , where a is the scale factor and α and ζ are parameters of the model. This phenomenological ansatz for ϕ can be motivated by generic solutions of a scalar dilaton field in many effective string theory and string-inspired gravity models in four dimensions. Most of the earlier discussions in the literature correspond to the choice that ζ = 0 so that ϕ(t) ∝ ln t or ϕ(t) ∝ ln a(t). Using a compilation of current data including type Ia supernovae, we impose observational constraints on the slope parameters like α and ζ and then discuss the relation of our results to analytical constraints on various cosmological parameters, including the dark energy equation of state. Some useful constraints are imposed on model parameters like α and ζ as well as on the dark energy/dark matter couplings using results from structure formation. The constraints of this model are shown to encompass the cosmological constant limit within 1σ error bars.