Fermion localization in a extra-dimensional $f(Q,\mathcal{T})$ gravity with cuscuton dynamics (2503.12187v1)

Abstract: We investigate the fermion localization in extra-dimensional $f(Q,\mathcal{T})$ gravity with cuscuton dynamics. This modified gravity theory is based on the nonmetricity scalar $Q$ and on the trace of the energy-momentum tensor $\mathcal{T}$. Using the first-order formalism we construct the complete brane system for three well-known superpotentials, namely the Sine-Gordon, the polynomial and the linear one. We show that the addition of the cuscuton term provides significant modifications to the structure of the brane. In particular, the scalar field solutions have the form of a kink-like structure, and the energy density is well localized, depending on both the modified-gravity and the cuscuton parameters. Furthermore, applying probabilistic measures, for the location of the fermions for a minimal Yukawa-type coupling we arrive at a Schr\"odinger-like equation allowing for a normalizable massless mode. Our solutions indicate strong brane localization only for left-chirality fermions. Moreover, the massive modes present solutions similar to free waves, which indicates that these fermions probably escape the brane. Finally, we find that massive fermions have a greater sensitivity to gravitational changes in the core of the brane, where oscillations with more pronounced amplitudes are present.