R 2 inflation to probe non-perturbative quantum gravity
Abstract It is natural to expect a consistent inflationary model of the very early Universe to be an effective theory of quantum gravity, at least at energies much less than the Planck one. For the moment, R + R 2, or shortly R 2, inflation is the most successful in accounting for the latest CMB dat...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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SpringerOpen
2018-03-01
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| Series: | Journal of High Energy Physics |
| Subjects: | |
| Online Access: | http://link.springer.com/article/10.1007/JHEP03(2018)071 |
| _version_ | 1818197778480758784 |
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| author | Alexey S. Koshelev K. Sravan Kumar Alexei A. Starobinsky |
| author_facet | Alexey S. Koshelev K. Sravan Kumar Alexei A. Starobinsky |
| author_sort | Alexey S. Koshelev |
| collection | DOAJ |
| description | Abstract It is natural to expect a consistent inflationary model of the very early Universe to be an effective theory of quantum gravity, at least at energies much less than the Planck one. For the moment, R + R 2, or shortly R 2, inflation is the most successful in accounting for the latest CMB data from the PLANCK satellite and other experiments. Moreover, recently it was shown to be ultra-violet (UV) complete via an embedding into an analytic infinite derivative (AID) non-local gravity. In this paper, we derive a most general theory of gravity that contributes to perturbed linear equations of motion around maximally symmetric space-times. We show that such a theory is quadratic in the Ricci scalar and the Weyl tensor with AID operators along with the Einstein-Hilbert term and possibly a cosmological constant. We explicitly demonstrate that introduction of the Ricci tensor squared term is redundant. Working in this quadratic AID gravity framework without a cosmological term we prove that for a specified class of space homogeneous space-times, a space of solutions to the equations of motion is identical to the space of backgrounds in a local R 2 model. We further compute the full second order perturbed action around any background belonging to that class. We proceed by extracting the key inflationary parameters of our model such as a spectral index (n s ), a tensor-to-scalar ratio (r) and a tensor tilt (n t ). It appears that n s remains the same as in the local R 2 inflation in the leading slow-roll approximation, while r and n t get modified due to modification of the tensor power spectrum. This class of models allows for any value of r < 0.07 with a modified consistency relation which can be fixed by future observations of primordial B-modes of the CMB polarization. This makes the UV complete R 2 gravity a natural target for future CMB probes. |
| first_indexed | 2024-12-12T01:55:23Z |
| format | Article |
| id | doaj.art-f2fa769cb4c145a8833324001ad9b7e3 |
| institution | Directory Open Access Journal |
| issn | 1029-8479 |
| language | English |
| last_indexed | 2024-12-12T01:55:23Z |
| publishDate | 2018-03-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Journal of High Energy Physics |
| spelling | doaj.art-f2fa769cb4c145a8833324001ad9b7e32022-12-22T00:42:24ZengSpringerOpenJournal of High Energy Physics1029-84792018-03-012018313710.1007/JHEP03(2018)071R 2 inflation to probe non-perturbative quantum gravityAlexey S. Koshelev0K. Sravan Kumar1Alexei A. Starobinsky2Departamento de Física and Centro de Matemática e Aplicações (CMA-UBI), Universidade da Beira InteriorDepartamento de Física and Centro de Matemática e Aplicações (CMA-UBI), Universidade da Beira InteriorL.D. Landau Institute for Theoretical Physics RASAbstract It is natural to expect a consistent inflationary model of the very early Universe to be an effective theory of quantum gravity, at least at energies much less than the Planck one. For the moment, R + R 2, or shortly R 2, inflation is the most successful in accounting for the latest CMB data from the PLANCK satellite and other experiments. Moreover, recently it was shown to be ultra-violet (UV) complete via an embedding into an analytic infinite derivative (AID) non-local gravity. In this paper, we derive a most general theory of gravity that contributes to perturbed linear equations of motion around maximally symmetric space-times. We show that such a theory is quadratic in the Ricci scalar and the Weyl tensor with AID operators along with the Einstein-Hilbert term and possibly a cosmological constant. We explicitly demonstrate that introduction of the Ricci tensor squared term is redundant. Working in this quadratic AID gravity framework without a cosmological term we prove that for a specified class of space homogeneous space-times, a space of solutions to the equations of motion is identical to the space of backgrounds in a local R 2 model. We further compute the full second order perturbed action around any background belonging to that class. We proceed by extracting the key inflationary parameters of our model such as a spectral index (n s ), a tensor-to-scalar ratio (r) and a tensor tilt (n t ). It appears that n s remains the same as in the local R 2 inflation in the leading slow-roll approximation, while r and n t get modified due to modification of the tensor power spectrum. This class of models allows for any value of r < 0.07 with a modified consistency relation which can be fixed by future observations of primordial B-modes of the CMB polarization. This makes the UV complete R 2 gravity a natural target for future CMB probes.http://link.springer.com/article/10.1007/JHEP03(2018)071Cosmology of Theories beyond the SMModels of Quantum Gravity |
| spellingShingle | Alexey S. Koshelev K. Sravan Kumar Alexei A. Starobinsky R 2 inflation to probe non-perturbative quantum gravity Journal of High Energy Physics Cosmology of Theories beyond the SM Models of Quantum Gravity |
| title | R 2 inflation to probe non-perturbative quantum gravity |
| title_full | R 2 inflation to probe non-perturbative quantum gravity |
| title_fullStr | R 2 inflation to probe non-perturbative quantum gravity |
| title_full_unstemmed | R 2 inflation to probe non-perturbative quantum gravity |
| title_short | R 2 inflation to probe non-perturbative quantum gravity |
| title_sort | r 2 inflation to probe non perturbative quantum gravity |
| topic | Cosmology of Theories beyond the SM Models of Quantum Gravity |
| url | http://link.springer.com/article/10.1007/JHEP03(2018)071 |
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