Calculable mass hierarchies and a light dilaton from gravity duals

Elander, Daniel; Piai, Maurizio

doi:10.1016/j.physletb.2017.06.035

Cited by 28 publications

(30 citation statements)

References 75 publications

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“…Papers on the dilaton in the context of holography have proliferated quite copiously, both in reference to the Goldberger-Wise (GW) stabilisation mechanism [49][50][51][52][53][54][55], as well as in dedicated studies of holographic models (see for example [56][57][58][59][60][61][62][63][64][65][66][67][68]), thanks in parts to the comparative ease with which systematic and rigorous calculations can be performed, within a wide variety of models. Within the rigorous top-down approach to holography, in which the gravity theory is derived from string theory or M-theory, in many cases the important long-distance properties are captured by a sigma-model theory coupled to gravity, that restricts the low-energy supergravity description to retain only a comparatively small number of degrees of freedom.…”

Section: Jhep06(2020)177mentioning

confidence: 99%

Probing the holographic dilaton

Elander

Piai

Roughley

2020

J. High Energ. Phys.

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Many strongly coupled field theories admit a spectrum of gauge-invariant bound states that includes scalar particles with the same quantum numbers as the vacuum. The challenge naturally arises of how to characterise them. In particular, how can a dilaton-the pseudo-Nambu-Goldstone boson associated with approximate scale invariance-be distinguished from other generic light scalars with the same quantum numbers? We address this problem within the context of gauge-gravity dualities, by analysing the fluctuations of the higher-dimensional gravitational theory. The diagnostic test that we propose consists of comparing the results of the complete calculation, performed by using gauge-invariant fluctuations in the bulk, with the results obtained in the probe approximation. While the former captures the mixing between scalar and metric degrees of freedom, the latter removes by hand the fluctuations that source the dilatation operator of the boundary fieldtheory. Hence, the probe approximation cannot capture a possible light dilaton, while it should fare well for other scalar particles. We test this idea on a number of holographic models, among which are some of the best known, complete gravity backgrounds constructed within the top-down approach to gauge-gravity dualities. We compute the spectra of scalar and tensor fluctuations, that are interpreted as bound states (glueballs) of the dual field theory, and we highlight those cases in which the probe approximation yields results close to the correct physical ones, as well as those cases where significant discrepancies emerge. We interpret the latter occurrence as an indication that identifying one of the lightest scalar states with the dilaton is legitimate, at least as a leading-order approximation.

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Section: Jhep06(2020)177mentioning

confidence: 99%

Probing the holographic dilaton

Elander

Piai

Roughley

2020

J. High Energ. Phys.

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“…Estimates based on Schwinger-Dyson equations, similar to the QCD ones [75], also indicate a low value for m σ [76], however the computation has been done for a Technicolor theory with f = v and cannot be extrapolated straightforwardly to our case. Gravitational dual results also indicate the lightest scalar mass is low compared to the other states [30,31]. All these results seem to point to the presence of a light scalar in theories near the conformal window.…”

Section: Tecni-σ Interpretationmentioning

confidence: 77%

“…[19] that the introduction of a lightish scalar resonance σ , that mixes with the pNGB Higgs, can alleviate the tension between EWPOs and the Technicolor vacuum. Increasing evidence of the presence of a light scalar state in theories with an infra-red conformal phase are being collected on the lattice [26][27][28][29], and by the use of gravitational duals [30,31] and of holographic models [32]. Such state, which may or may not be a dilaton, 1 necessarily mixes with the Higgs boson.…”

Section: Misalignement and Dynamicsmentioning

confidence: 99%

Sigma-assisted low scale composite Goldstone–Higgs

2020

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We show that the presence of a lightish scalar resonance, σ , that mixes with the composite Goldstone-Higgs boson can relax the typical bounds found in this class of models. This mechanism, inbred in models with a walking dynamics above the condensation scale, allows for a low compositeness scale f 400 GeV, corresponding to a misalignment angle s θ 0.6, contrary to the common lore of a smaller angle. According to recent lattice results, the light σ emerges thanks to a near-conformal phase above the condensation scale, consistent to the requirements from flavour physics. We study this effect in a general way, showing that it appears in all cosets emerging from an underlying gauge-fermion dynamics, in the presence of top partial compositeness. The scenario is testable both on the Lattice and experimentally, as it requires the presence of a second broad Higgs-like resonance, below 1 TeV, that can be revealed at the LHC in the Z Z and tt channels.

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“…This is an example in which the study of the relevant regular backgrounds in the gravity dual supports the existence in the field theory of a non-trivial spectrum exhibiting a parametrically light dilaton, that originates from multi-scale dynamics. The potential implications for phenomenology and model-building in the context of extensions of the standard model are highlighted elsewhere [77]. Among the many opportunities opened by this study, it would be interesting to know whether this model can be used to build semirealistic, calculable models for electroweak symmetry breaking, and whether the results of the model could be generalized to other backgrounds, possibly non-supersymmetric.…”

Section: Jhep06(2017)003mentioning

confidence: 96%

Glueballs on the baryonic branch of Klebanov-Strassler: dimensional deconstruction and a light scalar particle

Elander

Piai

2017

J. High Energ. Phys.

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Within gauge/gravity duality, we compute the scalar and tensor mass spectrum in the boundary theory defined by the five-dimensional sigma-model coupled to gravity obtained by constraining to eight scalars the truncation on T 1,1 that corresponds to the Papadopoulos-Tseytlin (PT) ansatz. We study fluctuations around the 1-parameter family of backgrounds that lift to the baryonic branch of the Klebanov-Strassler (KS) system, and interpolates between the KS background and the Maldacena-Nunez one (CVMN). We adopt a gauge invariant formalism in the treatment of the fluctuations that we interpret as states of the dual theory. The tensor spectrum interpolates between the discrete spectrum of the KS background and the continuum spectrum of the CVMN background, in particular showing the emergence of a finite energy range containing a dense set of states, as expected from dimensional deconstruction. The scalar spectrum shows analogous features, and in addition it contains one state that becomes parametrically light far from the origin along the baryonic branch.

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Calculable mass hierarchies and a light dilaton from gravity duals

Cited by 28 publications

References 75 publications

Probing the holographic dilaton

Probing the holographic dilaton

Sigma-assisted low scale composite Goldstone–Higgs

Glueballs on the baryonic branch of Klebanov-Strassler: dimensional deconstruction and a light scalar particle

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