Spinors Fields in Co-dimension One Braneworlds

Abstract

In this work we analyze the zero mode localization and resonances of $1/2-$spin fermions in co-dimension one Randall-Sundrum braneworld scenarios. We consider delta-like, domain walls and deformed domain walls membranes. Beyond the influence of the spacetime dimension $D$ we also consider three types of couplings: (i) the standard Yukawa coupling with the scalar field and parameter $\eta_1$, (ii) a Yukawa-dilaton coupling with two parameters $\eta_2$ and $\lambda$ and (iii) a dilaton derivative coupling with parameter $h$. Together with the deformation parameter $s$, we end up with five free parameter to be considered. For the zero mode we find that the localization is dependent of $D$, because the spinorial representation changes when the bulk dimensionality is odd or even and must be treated separately. For case (i) we find that in odd dimensions only one chirality can be localized and for even dimension a massless Dirac spinor is trapped over the brane. In the cases (ii) and (iii) we find that for some values of the parameters, both chiralities can be localized in odd dimensions and for even dimensions we obtain that the massless Dirac spinor is trapped over the brane. We also calculated numerically resonances for cases (ii) and (iii) by using the transfer matrix method. We find that, for deformed defects, the increasing of $D$ induces a shift in the peaks of resonances. For a given $\lambda$ with domain walls, we find that the resonances can show up by changing the spacetime dimensionality. For example, the same case in $D=5$ do not induces resonances but when we consider $D=10$ one peak of resonance is found. Therefore the introduction of more dimensions, diversely from the bosonic case, can change drastically the zero mode and resonances in fermion fields.Comment: 28 pages, 7 figure