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A Penrose limit for type IIB $AdS_6$ solutions

In this paper a Penrose limit is constructed for type IIB $AdS_6\times S^2\times Σ$ supergravity solutions. These solutions are dual to five dimensional SCFTs related to (p,q) five brane webs, which can often be described in terms of long quiver gauge theories. The null geodesic from which the Penrose limit is constructed is localized at a unique point on the two dimensional Riemann surface $Σ$, where the $AdS_6$ and $S^2$ metric factors are extremal. The resulting pp-wave spacetime takes a universal form. The world sheet action of the Green-Schwarz string is quadratic in the light cone gauge and the spectrum of string excitations is obtained.