Regge behavior saves String Theory from causality violations

Higher-derivative corrections to the Einstein-Hilbert action are present in bosonic string theory leading to the potential causality violations recently pointed out by Camanho et al.~cite{Camanho:2014apa}. We analyze in detail this question by considering high-energy string-brane collisions at impact parameters $b le l_s$ (the string-length parameter) with $l_s gg R_p$ (the characteristic scale of the D$p$-brane geometry). If we keep only the contribution of the massless states causality is violated for a set of initial states whose polarization is suitably chosen with respect to the impact parameter vector. Such violations are instead neatly avoided when the full structure of string theory --and in particular its Regge behavior-- is taken into account.