Equation Icon  ˙a 2 D¨k + 2 -D˙k − (4πG ¯ρ + ˙ϕ )Dk = 0, (74 ) a ( ) ¨ ˙a- D˙k- ˙ ϕk + 2 a + D ϕk = 0. (75 ) k