Dark Energy Constant: Is It Constant or Increasing?

[Einstein's Cat]

Is the amount of dark energy in the universe constant or else does it increase as the universe expands? In other words is the "anti- gravitational force" that is believed to be caused by dark energy and results in a accelerating universal expansion, a constant value or will it increase as the universe expands?

 

[Bandersnatch]

Yes, the fraction of dark energy as compared to matter and radiation in the universe increases as it expands.

 

[Einstein's Cat]

Yes, the fraction of dark energy as compared to matter and radiation in the universe increases as it expands.

Doesn't that mean that the cosmological constant isn't constant?

 

[PeterDonis]

Is the amount of dark energy in the universe constant or else does it increase as the universe expands?

What do you mean by "amount of dark energy"? The density of dark energy is constant. But the volume of the observable universe is increasing, so multiplying the constant density by the increasing volume gives an increasing total quantity of dark energy. However, the latter quantity isn't really meaningful physically; it's the density that matters.

Also, the density of ordinary matter, dark matter, and radiation is decreasing as the universe expands, so, as Bandersnatch said, the density of dark energy relative to the other densities is increasing. But that reflects a change in the other densities, not in the density of dark energy.

Doesn't that mean that the cosmological constant isn't constant?

No. The cosmological constant is equivalent to the density of dark energy, which is constant.