In this paper , time variable cosmological constant , dubbed age cosmological constant , is investigated motivated by the fact : any cosmological length scale and time scale can introduce a cosmological constant or vacuum energy density into Einstein ’ s theory .
The age cosmological constant takes the form \rho _ { \Lambda } = 3 c ^ { 2 } M ^ { 2 } _ { P } / t _ { \Lambda } ^ { 2 } , where t _ { \Lambda } is the age of our universe or conformal time .
The effective equation of state of age cosmological constant are w ^ { eff } _ { \Lambda } = -1 + \frac { 2 } { 3 } \frac { \sqrt { \Omega _ { \Lambda } } } { c } and w ^ { eff } _ { \Lambda } = -1 + \frac { 2 } { 3 } \frac { \sqrt { \Omega _ { \Lambda } } } { c } ( 1 + z ) when the age of universe and conformal time are taken as the role of cosmological time scales respectively .
They are the same as the so-called agegraphic dark energy models .
However , the evolution history are different from the agegraphic ones for their different evolution equations .