Intercommutation of U(1) global cosmic strings

Understand

Global strings (those which couple to Goldstone modes) may play a role in cosmology.

• In particular, if the QCD axion exists, axionic strings may control the efficiency of axionic dark matter abundance.
• The string network dynamics depend on the string intercommutation efficiency (whether strings re-connect when they cross).
• We point out that the velocity and angle in a collision between global strings "renormalize" between the network scale and the microscopic scale, and that this plays a significant role in their intercommutation dynamics.