Wormholes without exotic matter: does the choice of physics formula matter?

In modified gravity theories where geometry couples to matter, the choice of how you define 'matter Lagrangian' turns out to matter enormously: the same wormhole geometry can be threaded by different fluids, or identical fluids can produce different geometries. Working in f(Q,T) gravity, the authors find traversable, asymptotically flat wormholes that don't require exotic (negative-energy) matter across all tested Lagrangian choices. This highlights a genuine physical ambiguity in modified gravity that affects which solutions are considered physically viable.