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We discuss two types of instabilities which may arise in string theory compactified to asymptotically AdS spaces: perturbative, due to discrete modes in the spectrum of the Laplacian, and non-perturbative, due to brane nucleation. In the case of three dimensional Einstein manifolds, we completely characterize the presence of these instabilities, and in(More)
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(More)
We study a statistical model defined by a conformally invariant distribution of overlapping spheres in arbitrary dimension d. The model arises as the asymptotic distribution of cosmic bubbles in d + 1 dimensional de Sitter space, and also as the asymptotic distribution of bubble collisions with the domain wall of a fiducial “observation bubble” in d+ 2(More)
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