# Rotating Anisotropic universe

1. Feb 20, 2006

### wolram

2. Feb 20, 2006

### Garth

I always want to know what the universe is rotating with respect to?

This paper suggests the rotation shows up as the 'axis of evil' in the low l-mode WMAP anisotopy power spectrum. This axis can also be explained as the result of weak lensing of the CMB dipole by large scale structures in the local universe, see Local pancake defeats axis of evil.

Garth

3. Feb 20, 2006

### wolram

I asked a question some time ago about the possiblity that the universe
may be rotating, but does it need some (back ground) to rotate in respect
to? if it was rotating, would the total energy in the universe increase, i
suspect it must, how could the rotation rate be found? with no (back ground) to refer to.

4. Feb 21, 2006

### Garth

Who determines the 'background'?

Garth

5. Feb 21, 2006

### Labguy

Nobody could. And who would be "outside" to measure total angular momentum?

6. Feb 23, 2006

### Labguy

Question for you or anyone. I'm not much of a "Cosmo" guy as I am general astronomy and a bit more on stellar evolution (many would doubt). On the paper you mentioned above, when they say on page one that:
what do they mean by the term "ecliptic"? Our ecliptic is known to anybody but is there a galactic, local group or supercluster group ecliptic defined that I haven't been aware of? If they mean our ecliptic, it seems too much of a coincidence to be anything but a local effect and local even since the axis (both) point toward the Virgo cluster. On the scale of the universe even the Virgo cluster seems local to me.(?)

7. Feb 23, 2006

### George Jones

Staff Emeritus
Consider all the possible (timelike) geodesics for a non-interacting bunch of galaxies in a region of spacetime. These possible geodesics form a congruence, i.e., any event in the region lies on one, and only one, geodesic. Think of flow lines.

Roughly, the universe is rotating everywhere in the region if every geodesic in the congruence rotates about every other geodesic in the congruence. This is measurable. There is non-zero rotation when the the vorticity tensor $\omega_{ab} = \nabla_{\left[ a \right.} U_{\left. b \right]}$ is non-zero

Here:

1) $\nabla$ is the covariant derivative operator;
2) the square brackets denote an anti-symmetrizer;
3) $U$ is th (4-velocity) field of tangent vectors to the geodesics.

Regards,
George

Last edited: Jun 11, 2013