Matter pressure and vacuum pressure

[roopace]

how do I calculate the time when matter pressure and vacuum pressure add to 0 in the evolution of the universe. I have an exam of gravitation and cosmology coming Monday but have no clue where to start from. I can find nothing on weinberg and kolb and Turner textbooks

 

[mfb]

Calculate both as a function of time, set them equal (apart from their sign). You'll need some values of the current or earlier universe to start with. Which numbers can you use?