Inflation and reheating in theories with spontaneous scale invariance symmetry breaking

Rinaldi, Massimiliano; Vanzo, Luciano

doi:10.1103/physrevd.94.024009

Cited by 60 publications

(85 citation statements)

References 69 publications

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“…In this paper we analyse the inflationary properties of both the global and local scale invariant R + R 2 models. Our analysis simplifies previous studies of scale invariant R 2 inflation [23][24][25][26][27][28][29][30][31]. through the observation that "inertial" spontaneous Weyl symmetry breaking leads to the decoupling of the dilaton/Weyl photon and results in single field inflation with the second scalar being either a massless dilaton or providing the longitudinal component of a massive Weyl photon.…”

Section: Introductionmentioning

confidence: 58%

“…In this paper we are interested in a simpler possibility, generalising R + R 2 inflation to a scale independent form [23][24][25][26][27][28][29][30][31]. The Planck constraints on the inflationary observables are in remarkable agreement with the R + R 2 model of Starobinsky [32], proposed in 1980 and with a spectrum of CMB perturbations as analysed by Mukhanov and Chibisov [33] shortly afterwards.…”

Section: Introductionmentioning

confidence: 96%

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Scale-independent R2 inflation

et al. 2019

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Weyl (scale) invariant theories of scalars and gravity can generate all mass scales spontaneously. In this paper we study a particularly simple version -scale invariant R 2 gravity -and show that, during an inflationary period, it leads to fluctuations which, for a particular parameter choice, are almost indistinguishable from normal R 2 inflation. Current observations place tight constraints on the primary coupling constant of this theory and predict a tensor to scalar ratio, 0.0033 > r > 0.0026, which is testable with the next generation of cosmic microwave background experiments.

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Section: Introductionmentioning

confidence: 58%

Section: Introductionmentioning

confidence: 96%

Scale-independent R2 inflation

et al. 2019

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“…Here the "scalaron" mode is actually a compensator eaten by ω µ , while the matter field σ is the inflaton. Further, if there is no Weyl gauge field in (15), (set ω µ = 0), inflation is still possible and was already studied in [31]. The scenario is again similar to that in Starobinsky models.…”

Section: Canonical Action More Scalar Fields and Sm In Weyl Geometrymentioning

confidence: 88%

Stueckelberg breaking of Weyl conformal geometry and applications to gravity

Ghilencea

2020

Phys. Rev. D

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Weyl conformal geometry may play a role in early cosmology where effective theory at short distances becomes conformal. Weyl conformal geometry also has a built-in geometric Stueckelberg mechanism: it is broken spontaneously to Riemannian geometry after a particular Weyl gauge transformation (of "gauge fixing") while Stueckelberg mechanism re-arranges the degrees of freedom, conserving their number (n df ). The Weyl gauge field (ω µ ) of local scale transformations acquires a mass after absorbing a compensator (dilaton), decouples, and Weyl connection becomes Riemannian. Mass generation has thus a dynamic origin, corresponding to a transition from Weyl to Riemannian geometry. We show that a "gauge fixing" symmetry transformation of the original Weyl's quadratic gravity action in its Weyl geometry formulation, immediately gives the Einstein-Proca action for the Weyl gauge field and a positive cosmological constant, plus matter action (if present). As a result, the Planck scale is an emergent scale, where Weyl gauge symmetry is spontaneously broken and Einstein action is the broken phase of Weyl action. This is in contrast to local scale invariant models (no gauging) where a negative kinetic term (ghost dilaton) remains present and n df is not conserved when this symmetry is broken. The mass of ω µ , setting the non-metricity scale, can be much smaller than M Planck , for ultraweak values of the coupling (q), with implications for phenomenology. If matter is present, a positive contribution to the Planck scale from a scalar field (φ 1 ) vev induces a negative (mass) 2 term for φ 1 and spontaneous breaking of the symmetry under which it is charged. These results are immediate when using a Weyl geometry formulation of an action instead of its Riemannian picture. Briefly, Weyl gauge symmetry is physically relevant and its role in high scale physics should be reconsidered. *

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“…In cosmology there are global [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] or local [28][29][30][31][32][33][34][35][36][37][38][39] scale invariant alternatives to gravity with spontaneous breaking that generates the Planck scale by a non-minimal coupling.…”

Section: Motivationmentioning

confidence: 99%

Weyl R2 inflation with an emergent Planck scale

Ghilencea

2019

J. High Energ. Phys.

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We study inflation in Weyl gravity. The original Weyl quadratic gravity, based on Weyl conformal geometry, is a theory invariant under Weyl symmetry of (gauged) local scale transformations. In this theory Planck scale (M ) emerges as the scale where this symmetry is broken spontaneously by a geometric Stueckelberg mechanism, to Einstein-Proca action for the Weyl "photon" (of mass near M ). With this action as a "low energy" broken phase of Weyl gravity, long-held criticisms of the latter (due to non-metricity) are avoided. In this context, inflation with field values above M is natural, since this is just a phase transition scale from Weyl gravity (geometry) to Einstein gravity (Riemannian geometry), where the massive Weyl photon decouples. We show that inflation in Weyl gravity coupled to a scalar field has results close to those in Starobinsky model (recovered for vanishing non-minimal coupling), with a mildly smaller tensor-to-scalar ratio (r). Weyl gravity predicts a specific, narrow range 0.00257 ≤ r ≤ 0.00303, for a spectral index n s within experimental bounds at 68%CL and e-folds number N = 60. This range of values will soon be reached by CMB experiments and provides a test of Weyl

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Inflation and reheating in theories with spontaneous scale invariance symmetry breaking

Cited by 60 publications

References 69 publications

Scale-independent R2 inflation

Scale-independent R2 inflation

Stueckelberg breaking of Weyl conformal geometry and applications to gravity

Weyl R2 inflation with an emergent Planck scale

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