Posted: May 14, 2013 4:45 pm
by DavidMcC
Evolving wrote:Basically the two Nature articles (it is, in fact, two articles by physicists at the University of Massachusetts and at University College London) explain that a pear-shaped nucleus would tend to amplify a permanent electric dipole moment (EDM), if the nucleus had one in the first place. This would be significant, because the existence of a permanent EDM would break time symmetry as explained here:

To see why an EDM violates T symmetry, one has to consider the fact that a particle generally has a magnetic dipole moment (MDM), which can be thought of as being due to a tiny current flowing in a circle, or to the particle spinning. And there is a contribution to the particle’s energy that depends on the relative alignment of the EDM and the MDM. If T is reversed, the current flows in the opposite direction, so the MDM changes direction. But the EDM remains unchanged. So the alignment between the two has changed, the energy has changed and the symmetry is broken.

and if time symmetry is broken, then so must CP symmetry be (charge and parity), so that the whole system overall is CPT invariant. And CP asymmetry would, in turn, help in accounting for the overwhelming matter-antimatter asymmetry that we observe.

The odd thing about CP symmetry is that slight vioations of it are considered acceptable, as long as CPT symmetry remains intact. Could that be purely because it was long ago found that the electro-weak interaction violated CP, and nobody thought it odd?