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Interactions fondamentales, Astroparticules et Cosmologie
(11) Production(s) de l'année 2021


Vacuum stability conditions for Higgs potentials with SU(2)(L) triplets
Auteur(s): Moultaka G., Peyranère Michel
(Article) Publié:
Physical Review D, vol. 103 p.115006 (2021)
Texte intégral en Openaccess :
Ref HAL: hal03087658_v1
Ref Arxiv: 2012.13947
DOI: 10.1103/PhysRevD.103.115006
WoS: WOS:000661786800005
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
Résumé: Treelevel dynamical stability of scalar field potentials in renormalizable theories can in principle be expressed in terms of positivity conditions on quartic polynomial structures. However, these conditions cannot always be cast in a fully analytical resolved form, involving only the couplings and being valid for all field directions. In this paper we consider such forms in three physically motivated models involving SU (2) triplet scalar fields: the TypeII seesaw model, the GeorgiMachacek model, and a generalized twotriplet model. A detailed analysis of the latter model allows to establish the full set of necessary and sufficient boundedness from below conditions. These can serve as a guide, together with unitarity and vacuum structure constraints, for consistent phenomenological (treelevel) studies. They also provide a seed for improved looplevel conditions, and encompass in particular the leading ones for the more specific GeorgiMachacek case. Incidentally, we present complete proofs of various properties and also derive general positivity conditions on quartic polynomials that are equivalent but much simpler than the ones used in the literature.



Light dilaton in a metastable vacuum
Auteur(s): Elander D., Piai Maurizio, Roughley John
(Article) Publié:
Physical Review D, vol. 103 p.046009 (2021)
Texte intégral en Openaccess :
Ref HAL: hal03047633_v1
Ref Arxiv: 2011.07049
Ref INSPIRE: 1830179
DOI: 10.1103/PhysRevD.103.046009
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
Résumé: We identify a parametrically light dilaton by studying the perturbations of metastable vacua along a branch of regular supergravity backgrounds that are dual to fourdimensional confining field theories. The branch includes also stable and unstable solutions. The former encompass, as a special case, the geometry proposed by Witten as a holographic model of confinement. The latter approach a supersymmetric solution, by enhancing a condensate in the dual field theory. A phase transition separates the space of stable backgrounds from the metastable ones. In proximity of the phase transition, one of the lightest scalar states inherits some of the properties of the dilaton, despite not being particularly light.



Holographic models of composite Higgs in the Veneziano limit. Part I. Bosonic sector
Auteur(s): Elander D., Frigerio M., Knecht Marc, Kneur J.L.
(Article) Publié:
Journal Of High Energy Physics, vol. 03 p.182 (2021)
Texte intégral en Openaccess :
Ref HAL: hal03022749_v1
Ref Arxiv: 2011.03003
Ref INSPIRE: 1828484
DOI: 10.1007/JHEP03(2021)182
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
Résumé: We study stronglycoupled, approximately scaleinvariant gauge theories, which develop a mass gap in the infrared. We argue that a large number of fermion flavours is most suitable to provide an ultraviolet completion for the composite Higgs scenario. The holographic approach allows to describe the qualitative features of the nonperturbative dynamics in the Veneziano limit. We introduce new bottomup holographic models, which incorporate the backreaction of flavour on the geometry, and show that this can correlate the mass gap to the scale of flavoursymmetry breaking. We compute the mass spectrum for the various composite bosonic states, and study its dependence on the scaling dimension of the symmetrybreaking operators, as well as on the number of flavours. The different regions with a light dilaton are critically surveyed. We carefully assess the domain of validity of the holographic approach, and compare it with lattice simulations and the NambuJonaLasinio model.



Dilatonic states near holographic phase transitions
Auteur(s): Elander D., Piai Maurizio, Roughley John
(Article) Publié:
Physical Review D, vol. 103 p.106018 (2021)
Texte intégral en Openaccess :
Ref HAL: hal02981258_v1
Ref Arxiv: 2010.04100
Ref INSPIRE: 1821939
DOI: 10.1103/PhysRevD.103.106018
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
Résumé: The spectrum of bound states of special strongly coupled confining field theories might include a parametrically light dilaton, associated with the formation of enhanced condensates that break (approximate) scale invariance spontaneously. It has been suggested in the literature that such a state may arise in connection with the theory being close to the unitarity bound in holographic models. We extend these ideas to cases where the background geometry is nonAdS, and the gravity description of the dual confining field theory has a topdown origin in supergravity. We exemplify this programme by studying the circle compactification of Romans sixdimensional halfmaximal supergravity. We uncover a rich space of solutions, many of which were previously unknown in the literature. We compute the bosonic spectrum of excitations, and identify a tachyonic instability in a region of parameter space for a class of regular background solutions. A tachyon only exists along an energetically disfavoured (unphysical) branch of solutions of the gravity theory; we find evidence of a firstorder phase transition that separates this region of parameter space from the physical one. Along the physical branch of regular solutions, one of the lightest scalar particles is approximately a dilaton, and it is associated with a condensate in the underlying theory. Yet, because of the location of the phase transition, its mass is not parametrically small, and it is, coincidentally, the nexttolightest scalar bound state, rather than the lightest one.
