This work deals with braneworld models driven by real scalar fields with nonstandard dynamics. We develop the first-order formalism for models with standard gravity but with the scalar fields having generalized dynamics. We illustrate the results with examples of current interest, and we find analytical and numerical solutions for warp factors and scalar fields. The results indicate that the generalized braneworld scenario is classically stable, and capable of localizing gravity

We consider (4, 1)-dimensional branes constructed with two scalar fields $\varphi$ and $\chi$ coupled to a Dirac spinor field by means of a general Yukawa coupling. The equation of motion for the coefficients of the chiral decomposition of the spinor in curved spacetime leads to a Schrödinger-like equation whose solutions allow to obtain the masses of the fermionic modes. The simplest Yukawa coupling $\overline{\Psi }\varphi \chi \Psi$ is considered for the Bloch brane model and fermion localization is studied. We found resonances for both chiralities and related their appearance to branes with internal structure.

The CPT-even gauge sector of the standard model extension is composed of 19 components comprised in the tensor (KF)$\mu${}$\nu${}$\rho${}$\sigma${}, of which nine do not yield birefringence. In this work, we examine the Maxwell electrodynamics supplemented by these nine nonbirefringent CPT-even components in aspects related to the Feynman propagator and full consistency (stability, causality, unitarity). We adopt a prescription that parametrizes the nonbirefringent components in terms of a symmetric and traceless tensor, K$\mu${}$\nu${}, and second parametrization that writes K$\mu${}$\nu${} in terms of two arbitrary four-vectors, U$\mu${} and V$\nu${}. We then explicitly evaluate the gauge propagator of this electrodynamics in a tensor closed way. In the sequel, we show that this propagator and involved dispersion relations can be specialized for the parity-odd and parity-even sectors of the tensor (KF)$\mu${}$\nu${}$\rho${}$\sigma${}. In this way, we reassess some results of the literature and derive some new outcomes showing that the parity-even anisotropic sector engenders a stable, noncausal and unitary electrodynamics.