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Based on the conventional metric tensor and driven by a nearly constant energy density, cosmic inflation, characterized by a remarkably accelerated expansion, was proposed as an early epoch in the Universe. The energy density is typically…

General Relativity and Quantum Cosmology · Physics 2026-05-05 Swapnil K. Singh , Saleh O. Allehabi , Azzah A. Alshehri , Mahmoud Nasar , Abdel Nasser Tawfik

We investigate perturbations in power-law monomial potentials within inflationary models driven by a single scalar field. By introducing a second term to the original potential, we study how this perturbation influences the slow-roll…

General Relativity and Quantum Cosmology · Physics 2026-02-25 Maria E. S. Antunes , Micol Benetti , Eduardo Bittencourt , Fernando A. Franco

We build an inflationary model based on Degenerate Higher Order Scalar Tensor (DHOST) theories in a de Sitter background. We determine the scale-dependent power spectrum of curvature perturbations in these theories and we show that such a…

Cosmology and Nongalactic Astrophysics · Physics 2024-06-25 Andrei Lazanu

We examine the quantum loop effects on the single-field inflationary models in a spatially flat Friedmann-Robertson-Walker (FRW) cosmological space-time with a general self-interacting scalar field potential, which is modeled in terms of…

General Relativity and Quantum Cosmology · Physics 2020-02-05 Wei-Can Syu , Da-Shin Lee , Kin-Wang Ng

The single scalar field inflationary models that lead to scalar and tensor perturbation spectra with amplitudes varying in direct proportion to one another are reconstructed by solving the Stewart-Lyth inverse problem to next-to-leading…

Astrophysics · Physics 2009-11-07 C. A. Terrero-Escalante , James E. Lidsey , Alberto A. Garcia

We reinterpret Starobinsky's stochastic inflation as an open quantum system, where short-wavelength modes act as the environment for long-wavelength modes. Using the Schwinger-Keldysh formalism, we systematically trace out the environment…

High Energy Physics - Theory · Physics 2025-09-16 Yue-Zhou Li

We consider the backreaction of the long wavelength tensor modes produced during a slow-roll inflationary regime driven by a single scalar field in a spatially flat Friedmann-Lema\^{\i}tre-Robertson-Walker background geometry. We…

General Relativity and Quantum Cosmology · Physics 2014-08-27 G. Marozzi , G. P. Vacca

In a previous paper I showed that a classical scalar potential with $V''/V \sim 1$ can be sufficiently flattened by quantum corrections to give rise to slow-roll inflation. In this paper I give a hybrid inflation implementation of that idea…

High Energy Physics - Phenomenology · Physics 2016-08-24 Ewan D. Stewart

Quantum decoherence and the transition to semiclassical behavior during inflation has been extensively considered in the literature. In this paper, we use a simple model to analyze the same process in ekpyrosis. Our result is that the…

High Energy Physics - Theory · Physics 2013-05-30 Chien-Yao Tseng

We constrain cosmological models where the primordial perturbations have both an adiabatic and a (possibly correlated) cold dark matter (CDM) or baryon isocurvature component. We use both a phenomenological approach, where the primordial…

Cosmology and Nongalactic Astrophysics · Physics 2012-07-09 Jussi Valiviita , Matti Savelainen , Marianne Talvitie , Hannu Kurki-Suonio , Stanislav Rusak

We present a technique, {\em the uniform asymptotic approximation}, to construct accurate analytical solutions of the linear perturbations of inflation after quantum effects of the early universe are taken into account, for which the…

Cosmology and Nongalactic Astrophysics · Physics 2014-02-19 Tao Zhu , Anzhong Wang , Gerald Cleaver , Klaus Kirsten , Qin Sheng

In this work we construct a bottom-up reconstruction technique for Loop Quantum Cosmology scalar-tensor theories, from the observational indices. Particularly, the reconstruction technique is based on fixing the functional form of the…

General Relativity and Quantum Cosmology · Physics 2018-05-02 Jaume de Haro , S. D. Odintsov , V. K. Oikonomou

The Taylor expansion method has been used to investigate the scale dependence of the power spectrum of the curvature perturbation. In the present study, an alternative numerical method is used to clarify the $k$ dependence. Although there…

Cosmology and Nongalactic Astrophysics · Physics 2009-08-06 Shiro Hirai , Tomoyuki Takami

A sufficiently rigid relativistic elastic solid can be stable for negative pressure values and thus is capable of driving a stage of accelerated expansion. If a relativistic elastic solid drove an inflationary stage in the early Universe,…

Cosmology and Nongalactic Astrophysics · Physics 2014-07-02 Michael Sitwell , Kris Sigurdson

We review some recent progress in the extraction of inflationary observables in loop quantum cosmology. Inverse-volume quantum corrections induce a growth of power in the large-scale cosmological spectra and are constrained by observations.

General Relativity and Quantum Cosmology · Physics 2012-05-23 Gianluca Calcagni

Loop corrections to observables in slow-roll inflation are found to diverge no worse than powers of the log of the scale factor, extending Weinberg's theorem to quasi-single field inflation models. Demanding perturbation theory be valid…

High Energy Physics - Theory · Physics 2013-05-01 Klaus Larjo , David A. Lowe

We present a new method to calculate the spectrum of (slow-roll) inflationary perturbations, inspired by the conjectured dS/CFT correspondence. We show how the standard result for the spectrum of inflationary perturbations can be obtained…

High Energy Physics - Theory · Physics 2014-11-18 Jan Pieter van der Schaar

We set up a formalism that can be used to calculate the power spectrum of the curvature perturbations produced during inflation up to arbitrary order in the slow-roll expansion, and explicitly calculate the power spectrum and spectral index…

Astrophysics · Physics 2009-11-06 Ewan D. Stewart , Jin-Ook Gong

We study the modifications induced on scalar field inflation produced by considering a general modification of the Heisenberg algebra. We proceed by modifying the Poisson brackets on the classical theory whenever the corresponding quantum…

General Relativity and Quantum Cosmology · Physics 2024-08-13 H. Garcia-Compean , D. Mata-Pacheco

We investigate the one-loop quantum correction to the power spectrum of primordial curvature perturbations in the ultra-slow-roll (USR) inflationary scenario, incorporating the backreaction effect from curvature perturbations. In the…

General Relativity and Quantum Cosmology · Physics 2025-07-30 Cheng-Jun Fang , Zhen-Hong Lyu , Chao Chen , Zong-Kuan Guo