- #1

- 24,775

- 792

Unimodular Gravity was proposed by Einstein in 1919. It has the same equations of motion as ordinary GR, so you couldn't tell the difference experimentally. But time and the cosmological constant are treated differently in uni-GR from how they are in usual-GR. This may actually turn out to be an advantage.

So some people are working on quantizing unigrav---to get, among other aims, unigrav version of LQG and LQC (the full theory and it's application to cosmology.)

One simple way of looking at unigrav is that it is just the same as usual-GR except that the

And then you limit your diffeomorphisms to preserve that property.

It's not such a serious limitation. If you start with coords and a solution metric g

And that's not the only way to think about it.

Teitelboim was not the guy's original name. He had temporarily taken the name Teitelboim as a safety precaution because of the dangerous dictatorship in Chile. His real name was Bunster. Both are excellent-sounding names, and without doubt Bunster (aka Teitelboim) is both a lucky and creative individual.

The Henneaux Teitelboim action is shown on page 3 of http://arxiv.org/abs/1007.0735. It is equation (2.1)

So some people are working on quantizing unigrav---to get, among other aims, unigrav version of LQG and LQC (the full theory and it's application to cosmology.)

One simple way of looking at unigrav is that it is just the same as usual-GR except that the

**determinant of the metric must equal -1**---or anyway it must be constant.And then you limit your diffeomorphisms to preserve that property.

It's not such a serious limitation. If you start with coords and a solution metric g

_{µν}you can imagine stretching/squeezing the coords around each point to make the solution metric unimodular. Just mess with it some.And that's not the only way to think about it.

**You don't have to require the determinant g be constant.**There is some celebrated 1980s work by a Belgian and a Chilean (Henneaux and Teitelboim) which gave a general-covariant action for unigrav. So then any diffeomorphism was OK.Teitelboim was not the guy's original name. He had temporarily taken the name Teitelboim as a safety precaution because of the dangerous dictatorship in Chile. His real name was Bunster. Both are excellent-sounding names, and without doubt Bunster (aka Teitelboim) is both a lucky and creative individual.

The Henneaux Teitelboim action is shown on page 3 of http://arxiv.org/abs/1007.0735. It is equation (2.1)

Last edited: