Decoding the matrix: Coincident membranes on the plane wave

At the core of nonperturbative theories of quantum gravity lies the holographic encoding of bulk data in large matrices. At present this mapping is poorly understood. The plane wave matrix model provides a laboratory for isolating aspects of this problem in a controlled setting. At large boosts, configurations of concentric membranes become superselection sectors, whose exact spectra are known. From the bulk point of view one expects product states of individual membranes to be contained within the full spectrum. However, for non-BPS states this inclusion relation is obscured by Gauss law constraints. Its validity rests on nontrivial relations in representation theory, which we identify and verify by explicit computation.Comment: 43 pages, 2 figure

Matrix Theory for the DLCQ of Type IIB String Theory on the AdS/Plane-wave

We propose a recipe to construct the DLCQ Hamiltonian of type IIB string theory on the AdS (and/or plane-wave) background. We consider a system of J number of coincident unstable non-BPS D0-branes of IIB theory in the light-cone gauge and on the plane-wave background with a compact null direction, the dynamics of which is described by the world-line U(J) gauge theory. This configuration suffers from tachyonic instabilities. Having instabilities been cured through the process of open string tachyon condensation, by expanding the theory about true minima of the effective potential and furthermore taking low energy limit to decouple the heavy modes, we end up with a 0+1-dimensional supersymmetric U(J) gauge theory, a Matrix Theory. We conjecture that the Hamiltonian of this Matrix Theory is just the DLCQ Hamiltonian of type IIB string theory on the AdS or equivalently plane-wave background in a sector with J units of light-cone momentum. We present some pieces of evidence in support of the proposal.Comment: LaTeX, 35 pages, 2 eps figures; v2: minor changes, references added; v3: minor change

Compressible quantum phases from conformal field theories in 2+1 dimensions

Conformal field theories (CFTs) with a globally conserved U(1) charge Q can be deformed into compressible phases by modifying their Hamiltonian, H, by a chemical potential H -> H - \mu Q. We study 2+1 dimensional CFTs upon which an explicit S duality mapping can be performed. We find that this construction leads naturally to compressible phases which are superfluids, solids, or non-Fermi liquids which are more appropriately called `Bose metals' in the present context. The Bose metal preserves all symmetries and has Fermi surfaces of gauge-charged fermions, even in cases where the parent CFT can be expressed solely by bosonic degrees of freedom. Monopole operators are identified as order parameters of the solid, and the product of their magnetic charge and Q determines the area of the unit cell. We discuss implications for holographic theories on asymptotically AdS4 spacetimes: S duality and monopole/dyon fields play important roles in this connection.Comment: 30 pages, 2 figures; (v2) small corrections and more ref

Scattering in the adjoint sector of the c = 1 Matrix Model

Closed string tachyon emission from a traveling long string in Liouville string theory is studied. The exact collective field Hamiltonian in the adjoint sector of the c=1 matrix model is computed to capture the interaction between the tip of the long string and the closed string tachyon field. The amplitude for emission of a single tachyon quantum is obtained in a closed form using the chiral formalism.Comment: 22 pages, 2 figure

Is there a "most perfect fluid" consistent with quantum field theory?

It was recently conjectured that the ratio of the shear viscosity to entropy density, $\eta/ s$, for any fluid always exceeds $\hbar/(4 \pi k_B)$. This conjecture was motivated by quantum field theoretic results obtained via the AdS/CFT correspondence and from empirical data with real fluids. A theoretical counterexample to this bound can be constructed from a nonrelativistic gas by increasing the number of species in the fluid while keeping the dynamics essentially independent of the species type. The question of whether the underlying structure of relativistic quantum field theory generically inhibits the realization of such a system and thereby preserves the possibility of a universal bound is considered here. Using rather conservative assumptions, it is shown here that a metastable gas of heavy mesons in a particular controlled regime of QCD provides a realization of the counterexample and is consistent with a well-defined underlying relativistic quantum field theory. Thus, quantum field theory appears to impose no lower bound on $\eta/s$, at least for metastable fluids.Comment: 4 pages; typos corrected and references added in new versio

Conformal symmetry of brane world effective actions

A simple derivation of the low-energy effective action for brane worlds is given, highlighting the role of conformal invariance. We show how to improve the effective action for a positive- and negative-tension brane pair using the AdS/CFT correspondence.Comment: 5 pages, published versio

Gravity on a Little Warped Space

We investigate the consistent inclusion of 4D Einstein gravity on a truncated slice of AdS_5 whose bulk-gravity and UV scales are much less than the 4D Planck scale, M_* << M_{Pl}. Such "Little Warped Spaces" have found phenomenological utility and can be motivated by string realizations of the Randall-Sundrum framework. Using the interval approach to brane-world gravity, we show that the inclusion of a large UV-localized Einstein-Hilbert term allows one to consistently incorporate 4D Einstein gravity into the low-energy theory. We detail the spectrum of Kaluza-Klein metric fluctuations and, in particular, examine the coupling of the little radion to matter. Furthermore, we show that Goldberger-Wise stabilization can be successfully implemented on such spaces. Our results demonstrate that realistic low-energy effective theories can be constructed on these spaces, and have relevance for existing models in the literature.Comment: 1+24 page

Spiky Strings on NS5-branes

We study rigidly rotating strings in the near horizon geometry of a stack of Neveu-Schwarz (NS) 5-branes. We solve the Nambu-Goto action of the fundamental string in the presence of a NS-NS two form $(B_{\mu\nu})$ and find out limiting cases corresponding to magnon and spike like solutions.Comment: 10 pages, to appear in PL

Semiclassical Strings in AdS_5 x S^5 and Automorphic Functions

Using AdS/CFT we derive from the folded spinning string ordinary differential equations for the anomalous dimension of the dual N=4 SYM twist-two operators at strong coupling. We show that for large spin the asymptotic solutions have the Gribov-Lipatov recirocity property. To obtain this result we use a hidden modular invariance of the energy-spin relation of the folded spinning string. Further we identify the Moch-Vermaseren-Vogt (MVV) relations, which were first recognized in plain QCD calculations, as the recurrence relations of the asymptotic series ansatz.Comment: 4 page