Quintessence in a brane world
Abstract
We reanalyze a new quintessence scenario in a brane world model, assuming that a quintessence scalar field is confined in our threedimensional brane world. We study three typical quintessence models: (1) an inversepowerlaw potential, (2) an exponential potential, and (3) a kineticterm quintessence (kessence) model. With an inversepowerlaw potential model [V(φ)=μ^{α+4}φ^{α}], we show that in the quadratic dominant stage the density parameter of a scalar field Ω_{φ} decreases as a^{4(α2)/(α+2)} for 2<α<6, which is followed by the conventional quintessence scenario. This feature provides us wider initial conditions for successful quintessence. In fact, even if the universe is initially scalarfield dominated, it eventually evolves into a radiation dominated era in the ρ^{2}dominant stage. Assuming an equipartition condition, we discuss constraints on parameters, with the result that α>=4 is required. This constraint also restricts the value of the fivedimensional Planck mass, e.g., 4×10^{14}m_{4}<~m_{5}<~3×10^{13}m_{4} for α=5. For an exponential potential model V=μ^{4} exp(λφ/m_{4}), we may not find a natural and successful quintessence scenario as it is, while for a kineticterm quintessence, we find a tracking solution even in the ρ^{2}dominant stage, rather than the Ω_{φ}decreasing solution for an inversepowerlaw potential. Then we do find a slight advantage in a brane world. Only the density parameter increases more slowly in the ρ^{2}dominant stage, which provides a wider initial condition for successful quintessence.
 Publication:

Physical Review D
 Pub Date:
 December 2001
 DOI:
 10.1103/PhysRevD.64.123521
 arXiv:
 arXiv:hepph/0108012
 Bibcode:
 2001PhRvD..64l3521M
 Keywords:

 98.80.Cq;
 Particletheory and fieldtheory models of the early Universe;
 High Energy Physics  Phenomenology;
 Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory
 EPrint:
 17 pages, 9 figures, submitted to Physical Review D