Note on scale invariance and self-similar evolution in (3+1)-dimensional signum-Gordon model

Several classes of self-similar, spherically symmetric solutions of relativistic wave equation with nonlinear term of the form sign(\phi) are presented. They are constructed from cubic polynomials in the scale invariant variable t/r. One class of solutions describes a process of wiping out the initial field, another an accumulation of field energy in a finite and growing region of space.

💡 Research Summary

The paper investigates scale invariance and self‑similar evolution in the (3+1)‑dimensional signum‑Gordon model, whose field equation reads
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