# School of Physics

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Research Content for the School of Physics. Researchers in the School of the Physics.

For queries regarding content of Faculty of Science please contact Salome Potgieter by email : salome.potgieter@wits.ac.za or Tel : 011 717 1961

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### Browsing School of Physics by Subject "AdS-CFT Correspondence"

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Item Anomalous dimensions of heavy operators from magnon energies(Springer Verlag, 2016-03) de Mello Koch, R.; Tahiridimbisoa, N.H.; Mathwin, C.We study spin chains with boundaries that are dual to open strings suspended between systems of giant gravitons and dual giant gravitons. Motivated by a geometrical interpretation of the central charges of su(2|2), we propose a simple and minimal all loop expression that interpolates between the anomalous dimensions computed in the gauge theory and energies computed in the dual string theory. The discussion makes use of a description in terms of magnons, generalizing results for a single maximal giant graviton. The symmetries of the problem determine the structure of the magnon boundary reflection/scattering matrix up to a phase. We compute a reflection/scattering matrix element at weak coupling and verify that it is consistent with the answer determined by symmetry. We find the reflection/scattering matrix does not satisfy the boundary Yang-Baxter equation so that the boundary condition on the open spin chain spoils integrability. We also explain the interpretation of the double coset ansatz in the magnon language.Item Attractive holographic c -functions(Springer, 2014-11-24) Bhattacharyya, Arpan; Haque, S. Shajidul; Jejjala, Vishnu; Nampuri, Suresh; Véliz-Osorio, ÁlvaroUsing the attractor mechanism for extremal solutions in N = 2 gauged supergravity, we construct a c-function that interpolates between the central charges of theories at ultraviolet and infrared conformal fixed points corresponding to anti-de Sitter geometries. The c-function we obtain is couched purely in terms of bulk quantities and connects two different dimensional CFTs at the stable conformal fixed points under the RG flow.Item Heating up branes in gauged supergravity(Springer, 2014-08-26) Goldstein, Kevin; Nampuri, Suresh; V´eliz-Osorio, AlvaroIn this note, we explore the solution space of non-extremal black objects in 4D and 5D N = 2 gauged supergravity in the presence of fluxes. We present first order rewritings of the 4D action for a classes of non-extremal dyonic and electric solutions with electric flux backgrounds. Additionally, we obtain the non-extremal version of the Nernst brane in AdS 5 using a simple deformation. Finally, we develop a new technique to deform extremal black solutions in 4D to non-extremal solutions by an analysis of the symmetries of the equations of motion.Item Higher loop nonplanar anomalous dimensions from symmetry(Springer, 2014-02-28) Koch, Robert de Mello; Graham, Stuart; Messamah, IliesIn this article we study the action of the one loop dilatation operator on operators with a classical dimension of order N. These operators belong to the su(2) sector and are constructed using two complex fields Y and Z. For these operators non-planar diagrams contribute already at the leading order in N and the planar and large N limits are distinct. The action of the one loop and the two loop dilatation operator reduces to a set of decoupled oscillators and factorizes into an action on the Z fields and an action on the Y fields. Direct computation has shown that the action on the Y fields is the same at one and two loops. In this article, using the su(2) symmetry algebra as well as structural features of field theory, we give compelling evidence that the factor in the dilatation operator that acts on the Y s is given by the one loop expression, at any loop order.Item The hot attractor mechanism: decoupling without deep throats(Springer Verlag, 2016-04) Goldstein, K.; Jejjala, V.; Nampuri, S.Non-extremal black holes in (Formula presented.) supergravity have two horizons, the geometric mean of whose areas recovers the horizon area of the extremal black hole obtained from taking a smooth zero temperature limit. In prior work [1] using the attractor mechanism, we deduced the existence of several moduli independent invariant quantities obtained from averaging over a decoupled inter-horizon region. We establish that non-extremal geometries at the Reissner-Nordström point, where the scalar moduli are held fixed, can be lifted to solutions in supergravity with a near-horizon AdS3×S2. These solutions have the same entropy and temperature as the original black hole and therefore allow an interpretation of the underlying gravitational degrees of freedom in terms of CFT2. Symmetries of the moduli space enable us to explicate the origin of entropy in the extremal limit.Item Interactions as intertwiners in 4D QFT(Springer Verlag, 2016-03) de Mello Koch, R.; Ramgoolam, S.In a recent paper we showed that the correlators of free scalar field theory in four dimensions can be constructed from a two dimensional topological field theory based on so(4, 2) equivariant maps (intertwiners). The free field result, along with recent results of Frenkel and Libine on equivariance properties of Feynman integrals, are developed further in this paper. We show that the coefficient of the log term in the 1-loop 4-point conformal integral is a projector in the tensor product of so(4, 2) representations. We also show that the 1-loop 4-point integral can be written as a sum of four terms, each associated with the quantum equation of motion for one of the four external legs. The quantum equation of motion is shown to be related to equivariant maps involving indecomposable representations of so(4, 2), a phenomenon which illuminates multiplet recombination. The harmonic expansion method for Feynman integrals is a powerful tool for arriving at these results. The generalization to other interactions and higher loops is discussed.Item LLM magnons(Springer Verlag, 2016-03) de Mello Koch, R.; Mathwin, C.; Van Zyl, H.J.R.We consider excitations of LLM geometries described by coloring the LLM plane with concentric black rings. Certain closed string excitations are localized at the edges of these rings. The string theory predictions for the energies of magnon excitations of these strings depends on the radii of the edges of the rings. In this article we construct the operators dual to these closed string excitations and show how to reproduce the string theory predictions for magnon energies by computing one loop anomalous dimensions. These operators are linear combinations of restricted Schur polynomials. The distinction between what is the background and what is the excitation is accomplished in the choice of the subgroup and the representations used to construct the operator.Item Supergravity solutions with AdS(4) from non-Abelian T-dualities(Springer, 2016-02) Zayas, L.A.P.; Rodgers, V.G.J.; Whiting, C.A.We present a large class of new backgrounds that are solutions of type II supergravity with a warped AdS(4) factor, non-trivial axion-dilaton, B-field, and three-and five-form Ramond-Ramond fluxes. We obtain these solutions by applying non-Abelian T-dualities with respect to SU(2) or SU(2)/U(1) isometries to reductions to 10d IIA of 11d sugra solutions of the form AdS(4) x Y-7, with Y-7 = S-7/Z(k), S-7, M-1,M-1,M-1, Q(1,1,1) and N(1,1). The main class of reductions to IIA is along the Hopf fiber and leads to solutions of the form AdS(4) x K-6, where K-6 is Kahler Einstein with K-6 = CP3, S-2 x CP2, S-2 x S-2 x S-2; the first member of this class is dual to the ABJM field theory in the 't Hooft limit. We also consider other less symmetric but susy preserving reductions along circles that are not the Hopf fiber. In the case of N(1,1) we find an additional breaking of isometries in the NAT-dual background. To initiate the study of some properties of the field theory dual, we explicitly compute the central charge holographically.