Phase transitions from the fifth dimension

Abstract

We study the cosmological transition of 5D warped compactifications, from the high-temperature black-brane phase to the low-temperature Randall-Sundrum I phase. The transition proceeds via percolation of bubbles of IR-brane nucleating from the black-brane horizon. The violent bubble dynamics can be a powerful source of observable stochastic gravitational waves. While bubble nucleation is non-perturbative in 5D gravity, it is amenable to semiclassical treatment in terms of a “bounce” configuration interpolating between the two phases. We demonstrate how such a bounce configuration can be smooth enough to maintain 5D effective field theory control, and how a simple ansatz for it places a rigorous lower-bound on the transition rate in the thin-wall regime, and gives plausible estimates more generally. When applied to the Hierarchy Problem, the minimal Goldberger-Wise stabilization of the warped throat leads to a slow transition with significant supercooling. We demonstrate that a simple generalization of the Goldberger-Wise potential modifies the IR-brane dynamics so that the transition completes more promptly. Supercooling determines the dilution of any (dark) matter abundances generated before the transition, potentially at odds with data, while the prompter transition resolves such tensions. We discuss the impact of the different possibilities on the strength of the gravitational wave signals. Via AdS/CFT duality the warped transition gives a theoretically tractable holographic description of the 4D Composite Higgs (de)confinement transition. Our generalization of the Goldberger-Wise mechanism is dual to, and concretely models, our earlier proposal in which the composite dynamics is governed by separate UV and IR RG fixed points. The smooth 5D bounce configuration we introduce complements the 4D dilaton/radion dominance derivation presented in our earlier work.

String fragmentation in supercooled confinement and implications for dark matter

“…the dilaton [24]). That supercooling occurs with a light dilaton is known from a JHEP04(2021)278 number of previous studies [16][17][18], see [25][26][27][28][29][30][31][32][33] for studies in a confining sector and [34][35][36][37][38][39][40][41][42][43] for studies of holographic dual 5D warped extra dimension models.…”

Dark holograms and gravitational waves

“…In this appendix, we review the results of [21] that are used in order to compute the spectrum of gravitational waves. In [21], the confinement/deconfinement phase transition occurring in the WSS model was studied using an effective approach inspired by [28], and deployed in order to reduce the problem to a single-scalar one (a recent alternative approximation can be found in [63]). Moreover, the chiral symmetry breaking/restoration transition was described by the deformation of the D8 embedding, again encoded in a single scalar mode.…”

Gravitational waves from a holographic phase transition

“…Cosmological phase transitions in holographic models have been studied mostly in the context of Randall-Sundrum models [24][25][26][27][28][29][30][31][32][33][34][35][36][37], where there is a first order phase transition between a black brane geometry and a horizonless geometry. From the field theory dual point of view this is interpreted as a confinement transition [38].…”

“…Gravitational wave production has also been studied in Randall-Sundrum models [25,[30][31][32][34][35][36][37], and recently in the context of the above-mentioned Sakai-Sugimoto model [43]. It should be noted that all these studies are based on static configurations.…”