Abstract
Model building within the Randall-Sundrum (RS) framework generally involves placing the Standard Model fields in the bulk. Such fields may possess non-zero values for their associated brane-localized kinetic terms (BLKTs) in addition to possible bulk mass parameters. In this paper we clearly identify the regions of the RS model parameter space where the presence of bulk mass terms and BLKTs yield a setup which is free from both ghost and tachyon instabilities. Such physically acceptable parameter space regions can then be used to construct realistic and phenomenologically viable RS models.
Highlights
Required to be satisfied by any realistic model [7,8,9,10,11,12], one needs to be concerned about possible unphysical regions of the parameter space wherein ghost and/or tachyon states for the graviton or any of the SM fields may be present in the spectra [19]
In this paper we clearly identify the regions of the RS model parameter space where the presence of bulk mass terms and brane-localized kinetic terms (BLKTs) yield a setup which is free from both ghost and tachyon instabilities
In order to perform this analysis we first consider the case of a single fermion in the bulk, before electroweak symmetry breaking, with a bulk mass m = kν and possessing BLKTs on both the UV(IR) brane described by the parameters τ0(π), respectively
Summary
We provide a brief overview of the incorporation of bulk fermions in a generic. The bulk mass of Ψ is given by mfΨ = kνf , where νf is a dimensionless parameter that determines the location of the fermion fields in the bulk Note that this action includes generic brane-localized kinetic terms (BLKT’s) (i.e., represented by τ0 and τπ), which may arise due to loop effects or as a consequence of a UV completion of the theory for the left-handed, but not right-handed, fermion fields. This is by construction; in order to produce a left-handed chiral zero-mode, the left-handed five-dimensional field is required to be even under the orbifold’s Z2 symmetry, while the right-handed fields must.
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