Exceptional Waves and Characteristic Shocks on Non-Linear Relativistic Strings
Tommaso Ruggeri, Alberto Strumia · Progress of Theoretical Physics · 1978
Euler-Lagrange equations of a relativistic massive string are analyzed from the standpoint of non-linear wave propagation theory. Complete exceptionality is shown to hold, while strict exceptionality (usual in non-linear physical theories) appears only for non-vanishing value of the masses at the ends, when time-like or light-like gauge specification is employed.