Alexei A Starobinsky | Joint Institute for Nuclear Research (original) (raw)

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Papers by Alexei A Starobinsky

Research paper thumbnail of Joint reconstructions of growth and expansion histories from stage-IV surveys with minimal assumptions: Dark energy beyond Λ

Physical Review D

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Research paper thumbnail of Inflation with Sterile Scalar Coupled to Massive Fermions and to Gravity

Gravitation and Cosmology

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Research paper thumbnail of Massive scalar field in de Sitter spacetime: a two-loop calculation and a comparison with the stochastic approach

The European Physical Journal C

We examine long-wavelength correlation functions of massive scalar fields in de Sitter spacetime.... more We examine long-wavelength correlation functions of massive scalar fields in de Sitter spacetime. For the theory with a quartic self-interaction, the two-point function is calculated up to two loops. Comparing our results with the Hartree–Fock approximation and with the stochastic approach shows that the former resums only the cactus type diagrams, whereas the latter contains the sunset diagram as well and produces the correct result. We also demonstrate that the long-wavelength expectation value of the commutator of two fields is equal to zero both for spacelike and timelike separated points.

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Research paper thumbnail of Inflation story: slow-roll and beyond

Journal of Cosmology and Astroparticle Physics, 2021

We present constraints on inflationary dynamics and features in the primordial power spectrum of ... more We present constraints on inflationary dynamics and features in the primordial power spectrum of scalar perturbations using the Cosmic Microwave Background temperature, polarization data from Planck 2018 data release and updated likelihoods. We constrain the slow-roll dynamics using Hilltop Quartic Potential and Starobinsky R + R 2 model in the Einstein frame using the Planck 2018 binned Plik likelihood. Using the Hilltop as base potential, we construct Whipped Inflation potential to introduce suppression in the scalar power spectrum at large angular scales. We notice marginal (68% C.L.) preference of suppression from the large scale temperature angular power spectrum. However, large-scale E-mode likelihood based on high frequency instrument cross spectrum, does not support this suppression and in the combined data the preference towards the suppression becomes negligible. Based on the Hilltop and Starobinsky model, we construct the Wiggly Whipped Inflation potentials to introduce o...

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Research paper thumbnail of Whipped inflation

Motivated by the idea that inflation occurs at the GUT symmetry breaking scale, in this paper we ... more Motivated by the idea that inflation occurs at the GUT symmetry breaking scale, in this paper we construct a new class of large field inflaton potentials where the inflaton starts with a power law potential; after initial period of relative fast roll that lasts until after a few e-folds inside the horizon, it transits to the attractor of the slow roll part of the potential with a lower power. Due to the initial fast roll stages of inflation, we find a suppression in scalar primordial power at large scales and at the same time the choice of the potential can provide us a tensor primordial spectrum with high amplitude. This suppression in scalar power with a large tensor-to-scalar ratio helps us to reconcile the Planck and BICEP2 data in a single framework. We find that a transition from a cubic to quadratic form of inflaton potential generates an appropriate suppression in power of scalar primordial spectrum that provides significant improvement in fit compared to power law model whe...

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Research paper thumbnail of Anisotropic instability in a higher order gravity theory

Journal of Cosmology and Astroparticle Physics, 2020

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Research paper thumbnail of Analytic infinite derivative gravity, R2-like inflation, quantum gravity and CMB

International Journal of Modern Physics D, 2020

Emergence of [Formula: see text] inflation, which is the best fit framework for CMB observations ... more Emergence of [Formula: see text] inflation, which is the best fit framework for CMB observations till date, comes from the attempts to attack the problem of quantization of gravity which in turn have resulted in the trace anomaly discovery. Further developments in trace anomaly and different frameworks aiming to construct quantum gravity indicate an inevitability of nonlocality in fundamental physics at small time and length scales. A natural question would be to employ the [Formula: see text] inflation as a probe for signatures of nonlocality in the early Universe physics. Recent advances of embedding [Formula: see text] inflation in a string theory inspired nonlocal gravity modification provide very promising theoretical predictions connecting the nonlocal physics in the early Universe and the forthcoming CMB observations.

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Research paper thumbnail of Generating PBHs and small-scale GWs in two-field models of inflation

Journal of Cosmology and Astroparticle Physics, 2020

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Research paper thumbnail of Scalar-tensor theories of gravity, neutrino physics, and the H0 tension

Journal of Cosmology and Astroparticle Physics, 2020

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Research paper thumbnail of Probing features in the primordial perturbation spectrum with large-scale structure data

Monthly Notices of the Royal Astronomical Society, 2018

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Research paper thumbnail of Occurrence of exact R 2 inflation in non-local UV-complete gravity

Journal of High Energy Physics, 2016

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Research paper thumbnail of Primordial features and Planck polarization

Journal of Cosmology and Astroparticle Physics, 2016

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Research paper thumbnail of The screening Horndeski cosmologies

Journal of Cosmology and Astroparticle Physics, 2016

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Research paper thumbnail of Fast-roll inflation

A novel class of exact solutions of inflationary dynamics with a specific form of a scalar potent... more A novel class of exact solutions of inflationary dynamics with a specific form of a scalar potential is given based on a "fast-roll" ansatz, where the even-order slow-roll parameters approach to a nonnegligible constants while the odd ones are asymptotically vanishing in the quasi-de Sitter regime. Due to the rapid evolution of the background dynamics, the would-be decaying mode of the linear curvature perturbation may behave as a growing mode depending on the value of the model parameter, while the other mode remains constant. For the parameters giving a slightly red-tilted primordial power spectrum, the unwanted anomalous growth of the curvature perturbation is inevitable, which is similar to the case of the so-called ultra-slow-roll inflation.

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Research paper thumbnail of Observational Matter Power Spectrum and the Height of the Second Acoustic Peak

The Astrophysical Journal, 2001

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Research paper thumbnail of Steps toward the Power Spectrum of Matter. II. The Biasing Correction with σ 8 Normalization

The Astrophysical Journal, 1999

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Research paper thumbnail of Steps toward the Power Spectrum of Matter. I. The Mean Spectrum of Galaxies

The Astrophysical Journal, 1999

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Research paper thumbnail of A built-in scale in the initial spectrum of density perturbations: Evidence from cluster and CMB data

Journal of Experimental and Theoretical Physics Letters, 1997

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Research paper thumbnail of The cosmic web for density perturbations of various scales

Astronomy & Astrophysics, 2011

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Research paper thumbnail of Wiggly whipped inflation

Journal of Cosmology and Astroparticle Physics, 2014

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Research paper thumbnail of Joint reconstructions of growth and expansion histories from stage-IV surveys with minimal assumptions: Dark energy beyond Λ

Physical Review D

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Research paper thumbnail of Inflation with Sterile Scalar Coupled to Massive Fermions and to Gravity

Gravitation and Cosmology

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Research paper thumbnail of Massive scalar field in de Sitter spacetime: a two-loop calculation and a comparison with the stochastic approach

The European Physical Journal C

We examine long-wavelength correlation functions of massive scalar fields in de Sitter spacetime.... more We examine long-wavelength correlation functions of massive scalar fields in de Sitter spacetime. For the theory with a quartic self-interaction, the two-point function is calculated up to two loops. Comparing our results with the Hartree–Fock approximation and with the stochastic approach shows that the former resums only the cactus type diagrams, whereas the latter contains the sunset diagram as well and produces the correct result. We also demonstrate that the long-wavelength expectation value of the commutator of two fields is equal to zero both for spacelike and timelike separated points.

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Research paper thumbnail of Inflation story: slow-roll and beyond

Journal of Cosmology and Astroparticle Physics, 2021

We present constraints on inflationary dynamics and features in the primordial power spectrum of ... more We present constraints on inflationary dynamics and features in the primordial power spectrum of scalar perturbations using the Cosmic Microwave Background temperature, polarization data from Planck 2018 data release and updated likelihoods. We constrain the slow-roll dynamics using Hilltop Quartic Potential and Starobinsky R + R 2 model in the Einstein frame using the Planck 2018 binned Plik likelihood. Using the Hilltop as base potential, we construct Whipped Inflation potential to introduce suppression in the scalar power spectrum at large angular scales. We notice marginal (68% C.L.) preference of suppression from the large scale temperature angular power spectrum. However, large-scale E-mode likelihood based on high frequency instrument cross spectrum, does not support this suppression and in the combined data the preference towards the suppression becomes negligible. Based on the Hilltop and Starobinsky model, we construct the Wiggly Whipped Inflation potentials to introduce o...

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Research paper thumbnail of Whipped inflation

Motivated by the idea that inflation occurs at the GUT symmetry breaking scale, in this paper we ... more Motivated by the idea that inflation occurs at the GUT symmetry breaking scale, in this paper we construct a new class of large field inflaton potentials where the inflaton starts with a power law potential; after initial period of relative fast roll that lasts until after a few e-folds inside the horizon, it transits to the attractor of the slow roll part of the potential with a lower power. Due to the initial fast roll stages of inflation, we find a suppression in scalar primordial power at large scales and at the same time the choice of the potential can provide us a tensor primordial spectrum with high amplitude. This suppression in scalar power with a large tensor-to-scalar ratio helps us to reconcile the Planck and BICEP2 data in a single framework. We find that a transition from a cubic to quadratic form of inflaton potential generates an appropriate suppression in power of scalar primordial spectrum that provides significant improvement in fit compared to power law model whe...

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Research paper thumbnail of Anisotropic instability in a higher order gravity theory

Journal of Cosmology and Astroparticle Physics, 2020

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Analytic infinite derivative gravity, R2-like inflation, quantum gravity and CMB

International Journal of Modern Physics D, 2020

Emergence of [Formula: see text] inflation, which is the best fit framework for CMB observations ... more Emergence of [Formula: see text] inflation, which is the best fit framework for CMB observations till date, comes from the attempts to attack the problem of quantization of gravity which in turn have resulted in the trace anomaly discovery. Further developments in trace anomaly and different frameworks aiming to construct quantum gravity indicate an inevitability of nonlocality in fundamental physics at small time and length scales. A natural question would be to employ the [Formula: see text] inflation as a probe for signatures of nonlocality in the early Universe physics. Recent advances of embedding [Formula: see text] inflation in a string theory inspired nonlocal gravity modification provide very promising theoretical predictions connecting the nonlocal physics in the early Universe and the forthcoming CMB observations.

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Research paper thumbnail of Generating PBHs and small-scale GWs in two-field models of inflation

Journal of Cosmology and Astroparticle Physics, 2020

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Research paper thumbnail of Scalar-tensor theories of gravity, neutrino physics, and the H0 tension

Journal of Cosmology and Astroparticle Physics, 2020

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Research paper thumbnail of Probing features in the primordial perturbation spectrum with large-scale structure data

Monthly Notices of the Royal Astronomical Society, 2018

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Research paper thumbnail of Occurrence of exact R 2 inflation in non-local UV-complete gravity

Journal of High Energy Physics, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Primordial features and Planck polarization

Journal of Cosmology and Astroparticle Physics, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The screening Horndeski cosmologies

Journal of Cosmology and Astroparticle Physics, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Fast-roll inflation

A novel class of exact solutions of inflationary dynamics with a specific form of a scalar potent... more A novel class of exact solutions of inflationary dynamics with a specific form of a scalar potential is given based on a "fast-roll" ansatz, where the even-order slow-roll parameters approach to a nonnegligible constants while the odd ones are asymptotically vanishing in the quasi-de Sitter regime. Due to the rapid evolution of the background dynamics, the would-be decaying mode of the linear curvature perturbation may behave as a growing mode depending on the value of the model parameter, while the other mode remains constant. For the parameters giving a slightly red-tilted primordial power spectrum, the unwanted anomalous growth of the curvature perturbation is inevitable, which is similar to the case of the so-called ultra-slow-roll inflation.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Observational Matter Power Spectrum and the Height of the Second Acoustic Peak

The Astrophysical Journal, 2001

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Steps toward the Power Spectrum of Matter. II. The Biasing Correction with σ 8 Normalization

The Astrophysical Journal, 1999

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Research paper thumbnail of Steps toward the Power Spectrum of Matter. I. The Mean Spectrum of Galaxies

The Astrophysical Journal, 1999

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A built-in scale in the initial spectrum of density perturbations: Evidence from cluster and CMB data

Journal of Experimental and Theoretical Physics Letters, 1997

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The cosmic web for density perturbations of various scales

Astronomy & Astrophysics, 2011

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Wiggly whipped inflation

Journal of Cosmology and Astroparticle Physics, 2014

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