THE CIRCULAR LOOP EQUATION OF A COSMIC STRING WITH TIME-VARYING TENSION.

The equation of circular loops of cosmic string with time-dependent tension is studied in the Minkowski spacetime and Robertson–Walker universe. We found that, in the case where the tension depends on some power of the cosmic time, cosmic string loops with time-varying tension should not collapse to form a black hole if the power is lower than a critical value. [ABSTRACT FROM AUTHOR]