(p,q)-strings probing five-brane webs

In recent work, globally well-defined Type IIB supergravity solutions with geometry AdS6 × S2 warped over a Riemann surface Σ were constructed and conjectured to describe the near-horizon geometry of (p, q) five-brane webs in the conformal limit. In the present paper, we offer more evidence for this interpretation of the supergravity solutions in terms of five-brane webs. In particular, we explore the behavior of probe (p, q)-strings in certain families of these AdS6 × S2 × Σ backgrounds and compare this behavior to that predicted by microscopic, brane web considerations. In the microscopic picture, we argue that the embedding of a probe string may give rise to the formation of string junctions involving open strings anchored on the branes of the web. We then identify a quantity on the supergravity side that is conjectured to be equivalent to the total junction tension in a class of backgrounds corresponding to brane webs with four semi-infinite external five-branes. In the process, we will show that for general brane web backgrounds, the minimal energy probe string embeddings do not coincide with the embeddings preserving half of the background supersymmetries.