One more report from LIGO collaboration came up saying that no stochastic background gravitational waves were detected in the fourth science run. It is expected the existence of a background of gravitational waves, due to a large number of unresolved sources, coming from all directions in the sky. There are constraints on the spectrum of such waves coming from CMB, millisecond pulsars and other resonant detectors. It seems LIGO is sensitive enough to probe some models, like cosmic strings and pre-big bang models, for stochastic background gravitational waves. Unfortunatly no positive results were found.
Another interesting article appeared in New Scientist (subscription required) telling the history of the cosmic magnetic field. There is an intergalactic magnetic field whose origin is unknown. The known mechanisms to produce magnetic fields can not explain them. One possibility is that they were created long ago possibly during the inflation period . If this is true this primordial magnetic fields could provide a lot of information about the early universe. As it is explained in the article some experiments are now being set up to study this cosmic magnetic fields.