Dark energy models in the w-w' plane
Abstract
We examine the behavior of dark energy models in the plane defined by w (the equation of state parameter for the dark energy) and w' (the derivative of w with respect to the logarithm of the scale factor). For nonphantom barotropic fluids with positive squared sound speed, we find that w'<3w(w+1), the opposite of the bound on quintessence models previously derived by Caldwell and Linder. Thus, these barotropic models and quintessence models for the dark energy occupy disjoint regions in the w-w' plane. We also derive two new bounds for quintessence models in the w-w' plane: the first is a general bound for any scalar field with a monotonic potential, while the second improves on the Caldwell-Linder bound for tracker quintessence models. Observationally distinguishing barotropic models from quintessence models requires σ(w')≲1+w.
- Publication:
-
Physical Review D
- Pub Date:
- February 2006
- DOI:
- 10.1103/PhysRevD.73.043502
- arXiv:
- arXiv:astro-ph/0509890
- Bibcode:
- 2006PhRvD..73d3502S
- Keywords:
-
- 98.80.Cq;
- 95.36.+x;
- Particle-theory and field-theory models of the early Universe;
- Dark energy;
- Astrophysics;
- General Relativity and Quantum Cosmology;
- High Energy Physics - Theory
- E-Print:
- 5 pages, 3 figures, references and discussion added, to appear in Phys. Rev. D