We study superstring theories on AdS3 × N backgrounds yielding N = 2, 3, 4 extended superconformal symmetries in the dual boundary CFT. In each case the necessary constraints on the internal worldsheet theory N are found.

The symmetry operators for the Laplacian in flat space were recently described and here we consider the same question for the square of the Laplacian. Again, there is a close connection with conformal geometry. There are three main steps in our construction. The first is to show that the symbol of a symmetry is constrained by an overdetermined partial differential equation. The second is to sho...

We describe the unconventional infinite-dimensional Hopf superalgebra related to the integrable S-matrix of the AdS/CFT correspondence, and discuss its typical and atypical representations.

In recent work we showed that, for a class of conformal field theories (CFT) with Gauss-Bonnet gravity dual, the shear viscosity to entropy density ratio, eta/s, could violate the conjectured Kovtun-Starinets-Son viscosity bound, eta/s > or = 1/4 pi. In this Letter we argue, in the context of the same model, that tuning eta/s below (16/25)(1/4 pi) induces microcausality violation in the CFT, re...

We calculate the jet quenching parameter in medium with chemical potential from AdS/CFT correspondence. Our result is summarized in a plot. Moreover, we extract the explicit form of the jet quenching parameter of medium with small chemical potential for phases of dual SYM corresponding to large and small black holes. For the former phase, the jet quenching is increased as the charge density inc...

We consider string theory on a background of the form AdS 3 × N. Our aim is to give a description of the dual CFT in a general set up. With the requirement that we have N = 2 supersymmetry in spacetime, we provide evidence that the dual CFT is in the moduli space of a certain symmetric product M p /S p. On the way to show this, we reproduce some recent results on string propagation on AdS 3 and...

A survey of ideas, techniques and results from d=5 supergravity for the conformal and mass-perturbed phases of d=4 N=4 Super-Yang-Mills theory.

In this fourth paper of the series, I clarify the somewhat mysterious relation between the large class of orientation orbifolds (with twisted open-string CFT’s at ĉ = 52) and orientifolds (with untwisted open strings at c = 26), both of which have been associated to division by world-sheet orientation-reversing automorphisms. In particular – following a spectral clue in the previous paper – I s...

A conformal field theory (CFT) in dimension d≥3 coupled to a planar, two-dimensional, conformal defect is characterized in part by a "central charge" b that multiplies the Euler density in the defect's Weyl anomaly. For defect renormalization group flows, under which the bulk remains critical, we use reflection positivity to show that b must decrease or remain constant from the ultraviolet to t...