Warp factor and the gravitational wave spectrum

Abstract

A distinct signature of compact extra dimensions would be a Kaluza-Klein tower of gravitational waves. Motivated by this prospect, we compute the corresponding spectrum on a warped toroidal background. We evaluate in particular the impact of the warp factor on the spectrum. To that end, we use the complete warp factor H of standard string compactifications, generated by D-branes and orientifolds, thus connecting to recent works on stringy de Sitter constructions. The problematic region close to an orientifold where H < 0 leads to unphysical tachyonic modes in the spectrum. We develop tools that overcome this difficulty and lead to a tachyon-free spectrum. We show, in particular, that the warp factor can lower the first Kaluza-Klein mass by at least 69%.

Leaps and bounds towards scale separation

“…This property has allowed a relatively easy computation of the spin-two spectrum of many warped AdS vacua where a full diagonalization of the spectrum is currently out of reach; see for example [9,[28][29][30][31][32][33][34]. 7 Recent studies of how extra dimensions would influence gravity waves also include [37][38][39]. The effect of warping on KK reductions was also studied earlier in [40,41], and its connection with the problem of scale separation in [42].…”

Completing the D7-brane local gaugino action

“…string theory has been the subject of many interesting studies recently, see e.g. [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. We will not address these issues, including the particularly critical 'singular bulk problem' [24], which derives from the 'throat-gluing problem' of [14] and was recently treated further in [28,29].…”

“…[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. We will not address these issues, including the particularly critical 'singular bulk problem' [24], which derives from the 'throat-gluing problem' of [14] and was recently treated further in [28,29]. This is an issue specifically of KKLT and appears not to affect the LVS.…”

Leaps and bounds towards scale separation

“…This property has allowed a relatively easy computation of the spin-two spectrum of many warped AdS vacua where a full diagonalization of the spectrum is currently out of reach; see for example [9,[28][29][30][31][32][33][34]. 7 Recent studies of how extra dimensions would influence gravity waves also include [37][38][39]. The effect of warping on KK reductions was also studied earlier in [40,41].…”