We argue that type-II string theories contain unstable NS4-branes, which descend from a conjectured unstable M4-brane of M-theory. Assuming that an M2 brane can arise in M5-brane/anti-brane annihilation, the unstable M4 brane, and also an unstable M3-brane, must exist as sphalerons. We compare the tensions of the unstable NS4-branes, M4-brane, and related type-II unstable D-branes, and present lid supergravity solutions for unstable Mp-branes for all p. We study the ℤ2 gauge symmetry on the worldvolume of unstable branes, and argue that it can never be unbroken in the presence of lower brane charge.
ASJC Scopus subject areas
- Nuclear and High Energy Physics