Misaligned Supersymmetry and Open Strings

Understand

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-D$p$-brane placed on top of an O$p$-plane in type II string theory.
• Misaligned supersymmetry consists in cancellations between bosons and fermions at \emph{different} energy levels, in such a way that the averaged number of states grows at a rate dominated by a factor $\mathrm{e}^{C_{\mathrm{eff}}\sqrt{n}}$, with $C_{\mathrm{eff}}<C_{\mathrm{tot}}$, where $C_{\mathrm{tot}}$ is the inverse Hagedorn temperature.