In this article we use 5-brane junctions to study the 5D T _N SCFTs corresponding to the 5D \( \mathcal{N} \) = 1 uplift of the 4D \( \mathcal{N} \) = 2 strongly coupled gauge theories, which are obtained by compactifying N M5 branes on a sphere with three full punctures. Even though these theories have no Lagrangian description, by using the 5-brane junctions proposed by Benini, Benvenuti and Tachikawa, we are able to derive their Seiberg-Witten curves and Nekrasov partition functions. We cross-check our results with the 5D super-conformal index proposed by Kim, Kim and Lee. Through the AGTW correspondence, we discuss the relations between 5D superconformal indices and n-point functions of the q-deformed W _N Toda theories.

We show that the 5D Nekrasov partition functions enjoy the enhanced global symmetry of the UV fixed point. The fiber-base duality is responsible for the global symmetry enhancement. For SU(2) with N_f ≤ 7 flavors the fiber-base symmetry together with the manifest flavor SO(2N_f) symmetry generate the \( {\mathrm{E}}_{N_{f+1}} \) global symmetry, while in the higher rank case the manifest global symmetry of the two dual theories related by the fiber-base duality map generate the symmetry enhancement. The symmetry enhancement at the level of the partition function is manifest once we chose an appropriate reparametrization for the Coulomb moduli.

We calculate supersymmetric Wilson loops on the ellipsoid for a large class of \( \mathcal{N} \) = 2 SCFT using the localization formula of Hama and Hosomichi. From them we extract the radiation emitted by an accelerating heavy probe quark as well as the entanglement entropy following the recent works of Lewkowycz-Maldacena and Fiol-Gerchkovitz-Komargodski. Comparing our results with the \( \mathcal{N} \) = 4 SYM ones, we obtain interpolating functions f (g ²) such that a given \( \mathcal{N} \) = 2 SCFT observable is obtained by replacing in the corresponding \( \mathcal{N} \) = 4 SYM result the coupling constant by f (g ²). These "exact effective couplings" encode the finite, relative renormalization between the \( \mathcal{N} \) = 2 and the \( \mathcal{N} \) = 4 gluon propagator and they interpolate between the weak and the strong coupling. We discuss the range of their applicability.