Scalar fields on the bulk side of AdS/CFT correspondence can be assigned unconventional boundary conditions, related to the conventional one by Legendre transform. One can further perform double trace deformations which relate the two boundary conditions via renormalization group flow. Thinking of these operators as S and T transformations, respectively, we explore the SL(2, R) family of models which naively emerges from repeatedly applying these operations. Depending on the parameters, the effective masses vary and can render the theory unstable. However, unlike in the SL(2, Z) structure previously seen in the context of vector fields in AdS 4 , some of the features arising from this exercise, such as the vacuum susceptibility, turns out to be scheme dependent. We explain how scheme independent physical content can be extracted in spite of some degree of scheme dependence in certain quantities. arXiv:1709.00445v2 [hep-th]

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We analyze the dynamics of intersecting D3/D3' brane system overlapping in 1+1 dimensions, in a holographic treatment where N D3-branes are manifested as anti-de-Sitter Schwartzschild geometry, and the D3'-brane is treated as a probe. We extract the thermodynamic equation of state from the set of embedding solutions, and analyze the stability at the perturbative and the non-perturbative level. We review a systematic procedure to resolve local instabilities and multi-valuedness in the equations of state based on classic ideas of convexity in microcanonical ensumble. We then identify a run-away behavior which was not noticed previously for this system. arXiv:1509.04750v2 [hep-th]

We study the low energy effective theory of two sets of D3-branes overlapping in 1+1 dimensions, recently considered by Mintun, Polchinski, and Sun. In the original treatment by MPS, by studying the properties of magnetic solitons, the low energy effective field theory was found to require some ultraviolet completion, possibly involving full string dynamics. Recently in a companion paper, it was shown that by scaling the angle between the D3-branes and the D3 -branes in the zero slope limit in specific way, one can find simpler effective field theory which consists of a single tower of Regge trajectory states and yet is ultraviolet complete and non-singular. In this article, we study this model by further studying a limit which recovers the MPS dynamics from this non-singular construction. We approach this issue from a holographic perspective, where we consider a stack of N D3-branes overlapping with a single D3 -brane, and treat that D3 -brane as a probe in the AdS 5 × S 5 dual. In general, the D3 -brane probe supports a magnetic monopole as a non-singular soliton configuration, but in the limit where the MPS dynamics is recovered, the soliton degenerates. This is consistent with the idea that the effective dynamics in the MPS setup is incomplete, but that it can be completed with a single tower of Regge trajectory states.

We extend the analysis of boundedness and stability, initiated for scalar fields in anti de Sitter space in a previous work, to the case of vector fields. We show that the double trace deformation of Marolf and Ross is distinct from the double trace deformation of Witten. The former gives rise to an SL(2, R) family of theories whereas the latter gives rise to an independent SL(2, Z). We analyze the finite temperature two-point correlation function of current operators and infer the susceptibility and spectrum of low lying states. We discuss various physical features exhibited by these theories.