Early and Late Transient Cosmic Acceleration due to Curvature Inspired   Dark Energy
  It is obtained that dark energy emerges from higher-derivative gravity with anon-linear terms proportional to $R^2$ and $R^3$ with $R$ being the Ricci scalar curvature. Interestingly, it is found that the universe begins with acceleration, which continues for a short period. Later on,it decelerates driven by radiation and subsequently by matter. Two components of dark energy are found here.In the early universe, dark energy mimics quintessence giving high vlue of initial density $\sim 10^{75} {\rm GeV}^4$ at Planck scale. But, in the late universe, dark energy behaves like phantom giving current value of its density and causing late acceleration for some time. Thereafter, deceleration driven by matter resumes.Thus, two components of dark energy are obtained here (i) quintessence-like in the early universe and (ii)phantom-like in the late universe. Moreover, it is interesting to see acceleration being a transient phenomenon in early as well as late universe. 
S.K.Srivastava