No abstract

In this note we consider N = 4 SYM theories in 2+1 dimensions with gauge group U(N )×U(M ) and k hypermultiplets charged under the U(N ). When k > 2(N −M ), the theory flows to a superconformal fixed point in the IR. Theories with k < 2(N − M ), on the other hand, flows to strong coupling. We explore these theories from the perspective of gravity dual. We find that the gravity duals of theories with k < (N − M ) contain enhancons even in situations where repulson singularities are absent. We argue that supergravity description is unreliable in the region near these enhancon points. Instead, we show how to construct reliable sugra duals to particular points on the Coulomb branch where the enhancon is screened. We explore how these singularities reappear as one moves around in Coulomb branch and comment on possible field theory interpretation of this phenomenon. In analyzing gauge/gravity duality for these models, we encountered one unexpected surprise, that the condition for the supergravity solution to be reliable and supersymmetric is somewhat weaker than the expectation from field theory. We also discuss similar issues for theories with k = 0.

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]