AbstractIn this study, we propose an interacting model to explain the physical mechanism of the late time transition from matter-dominated era to the dark energy-dominated era of the Universe evolution and to obtain a scale factor a(t) representing two eras together. In the present model, we consider a minimal coupling of two scalar fields which correspond to the dark matter and dark energy interacting through a potential based on the FLRW framework. Analytical solution of this model leads to a new scale factor a(t) in the hybrid form $$a(t)=a_{0} (t/t_{0})^{\alpha } e^{ht/t_{0}}$$
a
(
t
)
=
a
0
(
t
/
t
0
)
α
e
h
t
/
t
0
. This peculiar result reveals that the scale factor behaving as $$a (t) \propto (t/t_{0})^{\alpha }$$
a
(
t
)
∝
(
t
/
t
0
)
α
in the range $$t/t_{0}\le t_{c}$$
t
/
t
0
≤
t
c
corresponds to the matter-dominated era while $$a(t) \propto \exp (ht/t_{0})$$
a
(
t
)
∝
exp
(
h
t
/
t
0
)
in the range $$t/t_{0}>t_{c}$$
t
/
t
0
>
t
c
accounts for the dark energy-dominated era, respectively. Surprisingly, we explore that the transition from the power-law to the exponential expansion appears at the crossover time $$t_{0} \approx 9.8$$
t
0
≈
9.8
Gyear. We attain that the presented model leads to precisely correct results so that the crossover time $$t_{0}$$
t
0
and $$\alpha $$
α
are completely consistent with the exact solution of the FLRW and re-scaled Hubble parameter $$H_{0}$$
H
0
lies within the observed limits given by Planck, CMB and SNIa data (or other combinations), which lead to consistent cosmological quantities such as the dimensionless Hubble parameter h, deceleration parameter q, jerk parameter j and EoS parameter w. We also discuss time dependent behavior of the dark energy and dark matter to show their roles on the time evolution of the universe. Additionally, we observe that all main results completely depend on the structure of the interaction potential when the parameter values are tuned to satisfy the zero energy condition. Finally, we conclude that interactions in the dark sector may play an important role on the time evolution and provides a mechanism to explain the late time transition of the Universe.
A MINIMAL MODEL FOR DILATONIC GRAVITY
