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5

In this answer we'll basically repeat Leandro M.'s good answer using formulas. Let us for simplicity use units where $c=1=\hbar$. Consider a spinless relativistic complex scalar field $$\tag{1} \left(\partial_t^2-\partial_x^2+m_0^2\right)\phi(x,t)~=~0$$ in 1+1 spacetime dimensions. The Lagrangian density for a spinless relativistic complex scalar field ...

13

A tachyon is a particle with an imaginary rest mass. This however does not mean it "travels" faster than light, nor that there's any conflict between their existence and the special theory of relativity. The main idea here is that the typical intuition we have about particles -- them being billiard ball-like objects -- utterly fails in the quantum world. It ...

-1

The problem is, that the word simultaneously means that the events are light-like connected. So, the flashing of two lights on your ribbon is not a space-like event. Tachyons behave very peculiar, i.e. in such a way that they lose energy while accelerating. It takes more and more energy to asymptotically slow them down towards the speed of light. It can ...

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