Fundamental questions such as emergence of geometry and gravitational dynamics from QFT amplitudes, barring specific examples, remain unanswered at the full stringy level in gauge-gravity duality. In this talk I will discuss recent progress toward a microscopic approach based on the worldline formulation of QFT. In particular, I will consider large-loop quantum corrections in holographic QFTs where internal propagators of Feynman diagrams are characterized by the Schwinger parameters and argue that embedding of string in the holographic coordinate emerges from the continuum limit of these Schwinger parameters at infinite loop limit. I will demonstrate, employing the techniques of Strebel differentials and discrete exterior calculus, how a worldsheet action for a bosonic string embedded in asymptotically AdS space-time could emerge from multi-loop Feynman graphs in a class of bosonic QFTs. I will end with a discussion of possible loopholes in this approach.

I will present a phenomenological model of the quark-gluon plasma that stem from 5 dimensional holography. The model is superior to the previous 5D models as it incorporates the running of the gauge coupling. It is constructed by requirements from QCD and a few lattice data. I will describe the transport properties of the quark-gluon plasma such as the bulk viscosity, energy loss of heavy quarks etc and their effects on the observables.