Chethan Krishnan

AdS4/CFT3 at one loop

I consider semi-classical type IIA strings rotating in the AdS 4 part of AdS 4 × ℂℙ 3. The one loop sigma model corrections to this classical solution are used to compute the energy shift, and the result is found to be E-S = f(λ)ln S with f(λ) = (√2λ) 1/2-(5ln 2/2π)+(1/√λ) 1/2). Even though the functional forms match, the actual numerical value of this one loop string result differs from the result obtained on the integrable N = 6 Chern-Simons (ABJM) theory side.

Membranes on calibrations

M2-branes can blow up into BPS funnels that end on calibrated intersections of M5-branes. In this quick note, we make the observation that the constraints required for the consistency of these solutions are automatic in Bagger-Lambert-Gustavsson (BLG) theory, thanks to the fundamental identity and the supersymmetry of the calibration. We use this to explain how the previous ad hoc fuzzy funnel constructions emerge in this picture, and make some comments about the role of the 3-algebra trace form in the derivation.

The black di-ring: an inverse scattering construction

We use the inverse scattering method (ISM) to derive concentric non-supersymmetric black rings. The approach used here is fully five dimensional, and has the modest advantage that it generalizes readily to the construction of more general axi-symmetric solutions.

AdS 4/CFT 3 at one loop

I consider semi-classical type IIA strings rotating in the AdS 4 part of AdS 4 × ℂℙ 3. The one loop sigma model corrections to this classical solution are used to compute the energy shift, and the result is found to be E-S = f(λ)ln S with f(λ) = (√2λ) 1/2-(5ln 2/2π)+(1/√λ) 1/2). Even though the functional forms match, the actual numerical value of this one loop string result differs from the result obtained on the integrable N = 6 Chern-Simons (ABJM) theory side.

A comment on Kerr–CFT and Wald entropy

Abstract We point out that the entropies of black holes in general diffeomorphism invariant theories, computed using the Kerr–CFT correspondence and the Wald formula (as implemented in the entropy function formalism), need not always agree. A simple way to illustrate this is to consider Einstein–Gauss–Bonnet gravity in four dimensions, where the Gauss–Bonnet term is topological. This means that the central charge of Kerr–CFT computed in the Barnich–Brandt–Compere formalism remains the same as in Einstein gravity, while the entropy computed using the entropy function gives a universal correction proportional to the Gauss–Bonnet coupling. We argue that at least in this example, the Kerr–CFT result is the physically reasonable one. The resolution to this discrepancy might lie in a better understanding of boundary terms.

The mesonic branch of the deformed conifold

Using coordinates that manifest the S2-S3 split of the base, we study D3-branes localized on the three-sphere in the Klebanov-Strassler background. We find a numerical solution for the warp factor and show the emergence of the AdS throat near the stack. In the dual gauge theory, this corresponds to an RG flow along the mesonic branch. We demonstrate how the cubic superpotential of the = 4 SYM theory emerges at the end of the RG flow.

Metastable black Saturns

Black Saturns have multiple horizons and so offer a testing ground for the ideas of black hole thermodynamics. In this note, we numerically scan for phases that are in equilibrium by extremizing total entropy in the 2-dimensional moduli space of stationary, singly rotating black Saturns with fixed total mass and angular momentum. On top of the known TH = TR, ΩH = ΩR configurations, we find phases that do not balance the temperature and angular velocity of the ring and the hole. But these (and most of the balanced Saturns) go away when we demand that the system is metastable, by imposing that the Hessian of the entropy is negative definite. Metastablity occurs when the dimensionless total angular momentum lies in a narrow window 0.92457 < j < 0.92463 of the thin ring branch. This is consistent with the expected range of classical stability of black Saturns and therefore may imply that thermal stability is tied to classical stability, in analogy with Gubser-Mitra in the translationally-invariant case. We also comment on the possibility of constructing plasma configurations that are dual to black Saturns in AdS.

Gauge Theory RG Flows from a Warped Resolved Orbifold

We study gauge-string duality of D3-branes localized at a point on the resolution of the ALE orbifold 3/3. By explicitly solving for the warp factor, we demonstrate the holographic RG flow from AdS5 × S5/3 (far away from the resolution) to the usual AdS5 × S5 (close to the stack). On the gauge theory side, this maps to the flow between the quiver gauge theory and = 4 super Yang-Mills. We present two possible scenarios for this RG flow depending on the choice of the VEVs. In particular, one of the scenarios proceeds by two steps involving both Higgsing and confinement.

Baryon dissociation in a strongly coupled plasma

Using the dual string theory, we study a circular baryonic configuration in a wind of strongly coupled = 4 Yang-Mills plasma blowing in the plane of the baryon, before and after a quark has dissociated from it. A simple enough model that captures many interesting features is when there are four quarks in the baryon. As a step towards phenomenology, we compare representative dissociated configurations, and make some comments about their energetics and other properties. Related results that we find include the observation that the screening length formula LsT ~ (1−v2)1/4 obtained previously for other color singlet configurations, is robust for circular baryons as well.

Cascading quivers from decaying D-branes

We use an argument analogous to that of Kachru, Pearson and Verlinde to argue that cascades in La,b,c quiver gauge theories always preserve the form of the quiver, and that all gauge groups drop at each step by the number M of fractional branes. In particular, we demonstrate that an NS5-brane that sweeps out the S3 of the base of La,b,c destroys M D3-branes.