Brane world cosmology: From superstring to cosmic strings

Brane inflation, where branes move towards each other, has been shown to be very robust. Inflation ends when branes collide and heat the universe. Towards the end of the brane inflationary epoch in the brane world, a complex tachyon field appears. As the tachyon rolls down its potential, cosmic strings (but not domain walls or monopoles) are copiously produced during brane collision. These cosmic strings are Dp-branes with (p - 1) dimensions compactified. Using the COBE data on the temperature anisotropy in the cosmic microwave background, the cosmic string tension p is estimated to be around G mu similar or equal to 10(-7). This in turn implies that the anisotropy in the cosmic microwave background comes mostly from inflation, but with a component (of order 10%) from cosmic strings. This can be tested by MAP and PLANCK. This cosmic string effect should also be observable in gravitational wave detectors like LIGO II/VIRGO and LISA.