Weyl $R^2$ inflation with an emergent Planck scale
| Autor: | D. M. Ghilencea |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
High Energy Physics - Theory
Nuclear and High Energy Physics Gravity (chemistry) Cosmology and Nongalactic Astrophysics (astro-ph.CO) FOS: Physical sciences General Relativity and Quantum Cosmology (gr-qc) Riemannian geometry 01 natural sciences General Relativity and Quantum Cosmology symbols.namesake High Energy Physics - Phenomenology (hep-ph) 0103 physical sciences Models of Quantum Gravity lcsh:Nuclear and particle physics. Atomic energy. Radioactivity 010306 general physics Mathematics::Representation Theory Gauge symmetry Mathematical physics Physics Inflation (cosmology) 010308 nuclear & particles physics Computer Science::Information Retrieval Proca action Cosmology of Theories beyond the SM Spon- taneous Symmetry Breaking Symmetry (physics) High Energy Physics - Phenomenology High Energy Physics - Theory (hep-th) symbols lcsh:QC770-798 Conformal geometry Scalar field Astrophysics - Cosmology and Nongalactic Astrophysics |
| Zdroj: | Journal of High Energy Physics Journal of High Energy Physics, Vol 2019, Iss 10, Pp 1-15 (2019) |
| Popis: | 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, century-old 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 $0.00257 \leq r\leq 0.00303$, 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 gravity. Unlike in the Starobinsky model, the prediction for $(r, n_s)$ is not affected by unknown higher dimensional curvature operators (suppressed by some large mass scale) since these are forbidden by the Weyl gauge symmetry. v3: 14 pages; Section 4 and references added |
| Databáze: | OpenAIRE |
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