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Toward Large N Thermal QCD from Dual Gravity: The Heavy Quarkonium Potential

We continue our study on the gravity duals for strongly coupled large N QCD with fundamental flavors both at zero and non-zero temperatures. The gravity dual at zero temperature captures the logarithmic runnings of the coupling constants at far IR and the almost conformal, albeit strongly coupled, behavior at the UV. The full UV completion of gauge theory is accomplished in the gravity side by attaching an AdS cap to the IR geometry described in our previous work. Attaching such an AdS cap is highly non-trivial because it amounts to finding the right interpolating geometry and sources that take us from a gravity solution with non-zero three-form fluxes to another one that has almost vanishing three-form fluxes. In this paper we give a concrete realisation of such a scenario, completing the program advocated in our earlier paper. One of the main advantage of having such a background, in addition to providing a dual description of the required gauge theory, is the absence of Landau poles and consequently the UV divergences of the Wilson loops. The potential for the heaviest fundamental quark anti-quark pairs, which are like the heavy quarkonium states in realistic QCD, can be computed and their linear behavior at large separations and zero temperature could be demonstrated. At small separations the expected Coulombic behavior appears to dominate. On the other hand, at non-zero temperatures interesting properties like heavy quarkonium type suppressions and melting are shown to emerge from our gravity dual. We provide some discussions of the melting temperature and compare our results with the Charmonium spectrum and lattice simulations. We argue that, in spite of the large N nature of our construction, certain model-independent predictions can be made.