In a nematic liquid crystal," Yurke notes, "you see many line-like defects, which correspond to cosmic strings, and you see a few point-like defects, which are monopoles.
Sometimes, strings that happen to cross each other snap in two, switch partners and reconnect -- an effect often seen in computer simulations of cosmic strings but never before observed in the laboratory, Yurke says.
Cosmic strings can lash back and forth at nearly the speed of light, for instance, whereas string-like defects in liquid crystals move as if they were immersed in molasses.
I had been working with cosmic strings for years, and here I finally got a chance to see them," Turok says.
Cosmic strings have no ends and would form either as closed loops or as infinitely long strands.
But recent computer simulations of the behavior of loops show that cosmic strings, if they exist, evolve in much more complicated ways than theorists had initially thought.
Vilenkin was among the first to propose that cosmic strings might explain clumping of matter into galaxies.
To complicate the picture further, theorists can also try to work out what happens when cosmic strings interact with cold dark matter or with massive neutrinos (known as hot dark matter).
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.
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.
Furthermore, if such expulsion and creation of particles by cosmic strings
really goes on, it could contribute a sizable amount to the total of dark matter that cosmologists think the universe needs in order to make it closed.