# Is the cosmological constant equivalent to vacuum energy?

1. Jul 27, 2011

### Naty1

Wikipedia says:

second paragraph here: http://en.wikipedia.org/wiki/Dark_energy

Vaccum energy (density) can vary over time and space???

Is that accurate? I've read the cosmological constant can vary, but not vacuum energy.

Last edited: Jul 27, 2011
2. Jul 28, 2011

### Nabeshin

I think you misread the quote. They say there are two kinds of dark energy: A true cosmological constant (in the sense of $\Lambda$ in Einstein's Equations), and then scalar fields. If the scalar fields DO NOT vary spatially, then we can lump them in with Einstein's cosmological constant. It is these scalar fields which are physically equivalent to the vacuum energy.

3. Jul 28, 2011

### Naty1

So the boldface quote is wrong:

Thanks.

4. Jul 29, 2011

### Demystifier

It's wrong, but it doesn't take much to rewrite it correctly:
The cosmological constant is physically equivalent to constant vacuum energy.