Misaligned supersymmetry and open strings

The study of non-supersymmetric string theories is shedding light on an important corner of the string landscape and might ultimately explain why, so far, we did not observe supersymmetry in our universe. We review how misaligned supersymmetry in closed-string theories leads to a cancellation between bosons and fermions even in non-supersymmetric string theories. We then show that the same cancellation takes place for open strings by studying an anti-Dp-brane placed on top of an Op-plane in type II string theory. Misaligned supersymmetry consists in cancellations between bosons and fermions at different energy levels, in such a way that the averaged number of states grows at a rate dominated by a factor eCeffn, with C-eff< C-tot, where C-tot is the inverse Hagedorn temperature. We prove the previously conjectured complete cancellation, i.e. we prove that C-eff = 0, for a vast class of models.

Automated summary

The study of non-supersymmetric string theories may provide insights into why supersymmetry has not been observed in our universe, shedding light on an important aspect of the string landscape. Investigation into misaligned supersymmetry in closed-string theories reveals cancellations between bosons and fermions, even in non-supersymmetric scenarios. Similarly, the same cancellation is observed for open strings through the study of an anti-Dp-brane placed on top of an Op-plane in type II string theory.