Getting vibes from cosmic strings.

Getting vibes from cosmic strings

Cosmic strings are defects in the structure of the universe,defects in space itself. They are leftovers from an earlier phase of cosmic existence in which space, the "vacuum,' had different properties. In modern physics, space can have properties analogous to those of matter, and it can undergo phase changes similar to the freezing or boiling of material substances. Cosmic strings are analogous to the crystal defects that occur when some liquid doesn't freeze exactly right.

The strings form loops carrying masses of 10(22) grams percentimeter of length and electrical supercurrents of 10(20) amperes. Weird as these strings sound, we many actually be seeing evidence of them, say three scientists residing in Princeton, N.J., Arif Babul and Bohdan Paczynski of Princeton University Observatory and David Spergel of the Institute for Advanced Study. In the May 15 ASTROPHYSICAL JOURNAL LETTERS they suggest that the bursts of high-energy gamma rays from unknown sources in the sky that detectors record from time to time may be from superconducting cosmic strings. This is the latest of several suggestions about the origin of these mysterious gamma rays.

As cosmic strings oscillate, certain fast-moving parts ofthem called "cusps' should produce narrow, well-directed beams of gamma rays that could give an observer crossing their path the effect of sharp bursts. If the energies and other parameters are right, we should see something like 100 such bursts a year. The cusps should also produce neutrinos and neutrons, and these, striking the upper atmosphere, should produce showers of secondary particles just as ordinary cosmic rays do. Babul, Paczynski and Spergel suggest that archival records of the world's cosmic ray shower detectors be searched for evidence of showers coincident with gamma ray bursts, which are recorded by orbiting satellites.