I have been wondering if strings in string theory can go faster than light, as it is one dimensional when it does not vibrate? So do the same limits apply to it, I googled it but could not find a straight answer, does anyone have an answer or article?
The longitudinal speed of a string is not a physical observable, due to reparametrization invariance, i.e. the points on a string are not material.
The transversal speed of a string does not exceed the speed of light $c$.
Free endpoints of an open string move with the speed of light $c$.
Concerning the presence of tachyonic fields, see e.g. this Phys.SE post.
- B. Zwiebach, A first course in String Theory, 2nd edition, 2009; Chapter 6.