It is possible to use ftl-travel with two space-time line-elements of second order in flat Minkoswki-spacetime.These line-elements are coupled via a third, variable factor,whose controlling allows to regulate the resulting line-element of fourth order.Setting the coupling-factor to zero, there remains classical SRT-line-element and both line-elements depart from each other.The case of ftl can be done by real restmass, so no classical tachyons are described but the case included possible

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... restenergy and negative kinetic-energy under special circumstances.For the case of appearing negativism, this is a function of the strength of the coupling-factor R, this negativism can be avoided by choosing a certain weak coupling strength.