Shearless curve breakup in the biquadratic nontwist map

Nontwist area-preserving maps violate the twist condition along shearless invariant curves, which act as transport barriers in phase space. Recently, some plasma models have presented multiple curves space and these can break up independently. In this paper, we describe different curve breakup scenarios of so-called biquadratic nontwist map, a recently proposed map derived from model, that captures essential behavior systems with curves. Three are found their dependence on system parameters is analyzed. The results indicate relation between periodic orbit reconnection-collision sequences. addition, even after breakup, remaining inhibit global transport.