محمد محمدی

‎Tachyons or hypothetical faster-than-light (FTL) particles would fail the principle of causality‎. ‎Such particles may only be imagined when they have no energy and momentum and‎, ‎thus‎, ‎no observable interaction‎. ‎In this paper‎, ‎we show that the classical relativistic field theory with non-standard Lagrangian densities (k-field models) does not rule out the existence of FTL particle-like solutions (solitons) with zero energy and momentum in 3+1 dimensions‎. However‎, ‎contrary to our expectation‎, ‎we show that it is possible to have k-field models that lead to energetic FTL soliton solutions in 3+1 dimensions‎.