### [astro-ph/0507110] Dynamical dark energy versus variable cos

Posted:

**July 06 2005**The authors look at implications of a varying \Lambda(t) and G(t). I do have some comments that are not ment as criticism to this paper (which has a different spirit), but rather as general remarks on the topic:

In a general covariant theory, there is no quantity \Lambda(t): general covariance implies that it must be a function of space time, hence \Lambda(t) -> \phi(x) and we are back at a scalar field theory.

Secondly, a change of Newton's constant G(t) and hence the Planck mass can be absorbed by a Weyl scaling. Of course, it is a matter of taste and convenience which frame might be more suitable. In principle, however, one can get rid of G(t) and will introduce an additional scalar field plus some matter-field couplings.

In a general covariant theory, there is no quantity \Lambda(t): general covariance implies that it must be a function of space time, hence \Lambda(t) -> \phi(x) and we are back at a scalar field theory.

Secondly, a change of Newton's constant G(t) and hence the Planck mass can be absorbed by a Weyl scaling. Of course, it is a matter of taste and convenience which frame might be more suitable. In principle, however, one can get rid of G(t) and will introduce an additional scalar field plus some matter-field couplings.