Why would there be math that had no physical manifestation? - Andrew Strominger

It is shown that many of the s of type II string theory and d = 11 supergravity can have boundaries on other p-branes. The rules for when this can and cannot occur are derived from charge conservation. For example it is found that membranes in d = 11 supergravity and IIA string theory can have boundaries on s. The boundary dynamics are governed by the self-dual d = 6 string. A collection of N parallel fivebranes contains 12N(N–1) self-dual strings which become tensionless as the fivebranes approach one another.

Much of over the last century has concerned the reductionist quest to uncover the laws of nature at ever shorter distances. In the last decade it has become increasingly clear, from a variety of investigations, that this long march into the has neglected a surprising wealth of uncharted phenomena in the deep (IR). Far from being a boring place where all is trivial and well-understood, the deep IR in four-dimensional Minkowski space has a rich structure which we are only beginning to understand. Applications range from the IR divergence problem in , 𝒩=4 Yang-Mills and color memory in in black hole information and a possible fundamental new perspective on space, time and nature.

Low-energy effective field theories arising from Calabi-Yau string compactifications are generically inconsistent or ill-defined at the classical level because of conifold singularities in the moduli space. It is shown, given a plausible assumption on the degenaracies of black hole states, that for type II theories this inconsistency can be cured by nonperturbative quantum effects: the singularities are resolved by the appearance of massless Ramond-Ramond black holes.