6 Riccion Inspired Quintessence like Dark Energy

In this letter, it is shown that dark energy is contributed by riccion (a particle concept for physical aspect of the Ricci scalar curvature) in a natural way without any input in the theory for it. In contrast to other models, where an idea for dark energy is introduced in the beginning of the theory, here it emerges from the gravitational sector spontaneously. Interestingly, it is found that dark energy density, obtained in this model, decreases with the scale factor a(t) as ∼ a(t) −3(1+w (de)) (where w (de) is the equation of state parameter for dark energy) explaining fall of its value from 1.19 × 10 75 GeV 4 at Planck scale to its present value suggested by recent experiments. Apart from dark energy, dark radiation also emerges from the gravity sector. It is demonstrated that the universe decelerates due to dominance of dark radiation upto the transition time 7.67 ± 1.5Gyr (for w (de) = −0.82) and accelerates later on due to dominance of dark energy. Moreover, it is found that value of the gravitational constant is slightly reduced at the cosmic scale due to acceleration. PACS no. 98.80.Cq