HYM-flation: Yang–Mills cosmology with Horndeski coupling

Давыдов, Evgeny A.; Gal’tsov, D.V.

doi:10.1016/j.physletb.2015.12.070

Cited by 18 publications

(24 citation statements)

References 59 publications

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“…Unlike Maxwell case, the vector Horndeski model with SU(2) Yang-Mills field admits homogeneous and isotropic cosmological solutions, including inflationary ones [17]. So here we consider the nonAbelian version of the action (34) The ansatz for metric in proper time gauge is standard:…”

Section: Homogeneous Isotropic Modelmentioning

confidence: 99%

“…Such configuration (with k = 0) in metric formulation was investigated in [17,18], so here we may focus on Palatini case. It is easy to calculate hyperstress (41) in O(λ) order, since then we may use Levi-Civita connection of the metric (43) instead of unknown affine connection.…”

Section: Homogeneous Isotropic Modelmentioning

confidence: 99%

“…Horndeski models, both in scalar [13] and vector [14] case have attracted a lot of interest in recent years, because the issues of inflation and/or dark energy can be resolved in a very natural way within their framework [15,16,17]. Although some of the models may be plagued by ghosts and instabilities [18], their elegant mathematical structure [19,20] motivates the detailed study.…”

Section: Introductionmentioning

confidence: 99%

“…One can find several studies of cosmological [25,26,17] and spherically symmetric [27,28] solutions to vector Horndeski theory in metric approach. But the Palatini version of the theory remains unexplored, to the best of our knowledge.Modified theories of gravitation with electromagnetic fields were pretty well studied in the Palatini approach [29,30,31], but in all the models examined, the interaction between matter and gravity was realized at the level of effective scalars with the lagrangians of the form: L = L(R, R ρσ R ρσ , F ρσ F ρσ , F ρσF ρσ ).…”

Section: Introductionmentioning

confidence: 99%

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Comparing metric and Palatini approaches to vector Horndeski theory

Давыдов

2018

Int. J. Mod. Phys. D

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We compare cosmologic and spherically symmetric solutions to metric and Palatini versions of vector Horndeski theory. It appears that Palatini formulation of the theory admits more degrees of freedom. Specifically, homogeneous isotropic configuration is effectively bimetric, and static spherically symmetric configuration contains non-metric connection. In general, the exact solution in metric case coincides with the approximative solution in Palatini case. The Palatini version of the theory appears to be more complicated, but the resulting non-linearity may be useful: we demonstrate that it allows the specific cosmological solution to pass through singularity, which is not possible in metric approach.

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Section: Homogeneous Isotropic Modelmentioning

confidence: 99%

Section: Homogeneous Isotropic Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparing metric and Palatini approaches to vector Horndeski theory

Давыдов

2018

Int. J. Mod. Phys. D

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“…The gauge models discussed above only include minimal couplings of the gauge fields, but non-minimal couplings are also possible [37,38]. However, couplings to the curvature that preserve the gauge symmetry are very delicate since one quickly runs into problems with Ostrogradski instabilities.…”

Section: Introductionmentioning

confidence: 99%

Instabilities in Horndeski-Yang-Mills inflation

et al. 2017

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A non-abelian SU (2) gauge field with a non-minimal Horndeski coupling to gravity gives rise to a de Sitter solution followed by a graceful exit to a radiation-dominated epoch. In this Horndeski YangMills (HYM) theory we derive the second-order action for tensor perturbations on the homogeneous and isotropic quasi de Sitter background. We find that the presence of the Horndeski non-minimal coupling to the gauge field inevitably introduces ghost instabilities in the tensor sector during inflation. Moreover, we also find Laplacian instabilities for the tensor perturbations deep inside the Hubble radius during inflation. Thus, we conclude that the HYM theory does not provide a consistent inflationary framework due to the presence of ghosts and Laplacian instabilities.

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Constant‐Roll Inflation in the Generalized SU(2) Proca Theory

et al. 2022

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The generalized SU(2) Proca theory (GSU2P) is a variant of the well known generalized Proca theory where the vector field belongs to the Lie algebra of the SU(2) group of global transformations under which the action is made invariant. New interesting possibilities arise in this framework because of the existence of new interactions of purely non-Abelian character and new configurations of the vector field resulting in spatial spherical symmetry and the cosmological dynamics being driven by the propagating degrees of freedom. We study the 2D phase space of the system that results when the cosmic triad configuration is employed in the Friedmann-Lemaitre-Robertson-Walker background and find an attractor curve whose attraction basin both covers almost all the allowed region and does not include a Big-Bang singularity. Such an attractor curve corresponds to a primordial inflationary solution that has the following characteristic properties: 1) it is a de Sitter solution whose Hubble parameter is regulated by a generalized version of the SU(2) group coupling constant, 2) it is constant-roll including, as a limiting case, the slow-roll variety, 3) a number of e-folds N > 60 is easily reached, 4) it has a graceful exit into a radiation dominated period powered by the canonical kinetic term of the vector field and the Einstein-Hilbert term. The free parameters of the action are chosen such that the tensor sector of the theory is the same as that of general relativity at least up to second-order perturbations, thereby avoiding the presence of ghost and Laplacian instabilities in the tensor sector as well as making the gravity waves propagate at light speed. This is a proof of concept of the interesting properties that could be found in this scenario when the coupling constants be replaced by general coupling functions and more terms be discovered in the GSU2P.

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HYM-flation: Yang–Mills cosmology with Horndeski coupling

Cited by 18 publications

References 59 publications

Comparing metric and Palatini approaches to vector Horndeski theory

Comparing metric and Palatini approaches to vector Horndeski theory

Instabilities in Horndeski-Yang-Mills inflation

Constant‐Roll Inflation in the Generalized SU(2) Proca Theory

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