Unbounded entropy in spacetimes with positive cosmological constant

In theories of gravity with a positive cosmological constant, we consider product solutions with flux, of the form (A)dS_p x S^q. Most solutions are shown to be perturbatively unstable, including all uncharged dS_p x S^q spacetimes. For dimensions greater than four, the stable class includes universes whose entropy exceeds that of de Sitter space, in violation of the conjectured "N-bound". Hence, if quantum gravity theories with finite-dimensional Hilbert space exist, the specification of a positive cosmological constant will not suffice to characterize the class of spacetimes they describe.Comment: 25 pages; v2: references adde

Dynamic critical phenomena at a holographic critical point

We study time-dependent perturbations to a family of five-dimensional black hole spacetimes constructed as a holographic model of the QCD phase diagram. We use the results to calculate two transport coefficients, the bulk viscosity and conductivity, as well as the associated baryon diffusion constant, throughout the phase diagram. Near the critical point in the T-mu plane, the transport coefficients remain finite, although their derivatives diverge, and the diffusion goes to zero. This provides further evidence that large-N_c gauge theories suppress convective transport. We also find a divergence in the low-temperature bulk viscosity, outside the region expected to match QCD, and compare the results to the transport behavior of known R-charged black holes.Comment: 40 pages, 11 figures, LaTe

New Attractors and Area Codes

In this note we give multiple examples of the recently proposed New Attractors describing supersymmetric flux vacua and non-supersymmetric extremal black holes in IIB string theory. Examples of non-supersymmetric extremal black hole attractors arise on a hypersurface in $WP^{4}_{1,1,1,1,2}$. For flux vacua on the orientifold of the same hypersurface existence of multiple basins of attraction is established. It is explained that certain fluxes may give rise to multiple supersymmetric flux vacua in a finite region on moduli space, say at the Landau-Ginzburg point and close to conifold point. This suggests the existence of multiple basins for flux vacua and domain walls in the landscape for a fixed flux and at interior points in moduli space.Comment: 16 pages, harvmac. v2: acknowledgement update

Affine 7-brane Backgrounds and Five-Dimensional ENE_N Theories on S1S^1

Elliptic curves for the 7-brane configurations realizing the affine Lie algebras \wh E_n $(1 \leq n \leq 8)$ and \wh{\wt E}_n $(n=0,1)$ are systematically derived from the cubic equation for a rational elliptic surface. It is then shown that the \wh E_n 7-branes describe the discriminant locus of the elliptic curves for five-dimensional (5D) N=1 $E_n$ theories compactified on a circle. This is in accordance with a recent construction of 5D N=1 $E_n$ theories on the IIB 5-brane web with 7-branes, and indicates the validity of the D3 probe picture for 5D $E_n$ theories on \bR^4 \times S^1. Using the \wh E_n curves we also study the compactification of 5D $E_n$ theories to four dimensions.Comment: 23 pages, Latex, no figures, some statements clarified, typos corrected, references and note adde