Joint Theory Seminar: Ronnie Rodgers

Title: Holographic defect entropy and monotonicity

Abstract: C-functions are quantities in quantum field theory (QFT) that monotonically decrease under renormalisation group flows, thus making quantitative the notion of reduction of degrees of freedom along the flow. One way to define C-functions and prove their monotonicity is using entanglement entropy. I will review how holography can be used to obtain entropic C-functions for large-N, strongly coupled QFTs, and show an explicit example from my recent work. The QFT in my example is (3+1)-dimensional N=4 supersymmetric Yang-Mills theory coupled to hypermultiplets localised to a (2+1)-dimensional planar defect, with an RG flow triggered by a non-zero hypermultiplet mass. The gravity dual consists of probe D5-branes in AdS5 x S5. I will also discuss the case of an interface - where the rank of the gauge group is different on either side of the defect.