### [astro-ph/0602377] Anisotropic perturbations due to dark ene

Posted:

**April 03 2006**This is an interesting paper, which investigates whether elastic (solid) dark energy could give rise to large scale anisotropies in the observed CMB. An interesting feture is that coupling between scalar, vector and tensor modes is generated by breaking rotational invariance via the anisotropic elasticity tensor.

The model is in some tension with other (e.g. supernova) data because it requires a dark energy equation of state w=-2/3.

Their general Lagrangian is specified so that it is only a function of the metric. Since the action should be gauge invariant, and the gauge invariant function of the metric tensor is the Riemann tensor, does this mean that their model is equivalent to a generalized gravity theory with some f(R_{abcd}) action?

The model is in some tension with other (e.g. supernova) data because it requires a dark energy equation of state w=-2/3.

Their general Lagrangian is specified so that it is only a function of the metric. Since the action should be gauge invariant, and the gauge invariant function of the metric tensor is the Riemann tensor, does this mean that their model is equivalent to a generalized gravity theory with some f(R_{abcd}) action?