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We revisit the one-loop correction in curvature perturbation power spectrum in models of single field inflation which undergo a phase of ultra slow-roll (USR) inflation. We include the contributions from both the cubic and quartic…

Cosmology and Nongalactic Astrophysics · Physics 2023-10-06 Hassan Firouzjahi

The nature of one-loop corrections to long-wavelength CMB-scale modes in single-field inflation models with an intermediate USR phase remains a subject of active debate. In this work, we perform a detailed investigation into the…

Cosmology and Nongalactic Astrophysics · Physics 2025-08-29 Haidar Sheikhahmadi , Amin Nassiri-Rad

We calculate the one-loop corrections in bispectrum of CMB scale perturbations induced from the small scale modes undergoing an intermediate phase of USR inflation in scenarios employed for PBHs formation. Using the formalism of effective…

Cosmology and Nongalactic Astrophysics · Physics 2024-09-18 Hassan Firouzjahi

An estimate of the one-loop correction to the power spectrum of the primordial curvature perturbation is given, assuming it is generated during a phase of single-field, slow-roll inflation. The loop correction splits into two parts, which…

Astrophysics · Physics 2010-02-09 David Seery

We discuss the issue of perturbativity in single-field inflationary models with a phase of ultra slow-roll (USR) tailor suited to generate an order-one abundance of primordial black holes (PBHs). More in detail, we impose the condition that…

Cosmology and Nongalactic Astrophysics · Physics 2024-07-01 Gabriele Franciolini , Antonio Junior Iovino , Marco Taoso , Alfredo Urbano

Calculating the action and the interaction Hamiltonian at higher orders in cosmological perturbation theory is a cumbersome task. We employ the formalism of EFT of inflation in the decoupling limit for single-field ultra slow-roll (USR)…

Cosmology and Nongalactic Astrophysics · Physics 2026-05-15 Hassan Firouzjahi , Bahar Nikbakht

We study the one-loop corrections in power spectrum of long gravitational waves induced from small scale modes in the models of single field inflation undergoing a phase of ultra-slow-roll (USR). We show that the spectrum of long tensor…

Cosmology and Nongalactic Astrophysics · Physics 2024-12-05 Hassan Firouzjahi

We calculate the two-loop corrections in primordial power spectrum in models of single field inflation incorporating an intermediate USR phase employed for PBHs formation. Among the total eleven one-particle irreducible Feynman diagrams, we…

High Energy Physics - Phenomenology · Physics 2024-12-16 Hassan Firouzjahi

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

Single-field models of inflation might lead to amplified scalar fluctuations on small scales due, for example, to a transient ultra-slow-roll phase. It was argued by Kristiano $\&$ Yokoyama in arXiv:2211.03395 that the enhanced amplitude of…

Cosmology and Nongalactic Astrophysics · Physics 2024-05-15 Matthew W. Davies , Laura Iacconi , David J. Mulryne

We re-examine the importance of slow-roll corrections during the evolution of cosmological perturbations in models of multi-field inflation. We find that in many instances the presence of light degrees of freedom leads to situations in…

Cosmology and Nongalactic Astrophysics · Physics 2012-02-28 Anastasios Avgoustidis , Sera Cremonini , Anne-Christine Davis , Raquel H. Ribeiro , Krzysztof Turzynski , Scott Watson

We calculate the action and the interaction Hamiltonians to all orders in perturbation theory in the model of single field inflation with a transient ultra slow-roll phase. Employing the formalism of EFT of inflation, we obtain a compact…

Cosmology and Nongalactic Astrophysics · Physics 2026-05-15 Hassan Firouzjahi , Bahar Nikbakht

We examine one-loop corrections from small-scale curvature perturbations to the superhorizon-limit ones in single-field inflation models, which have recently caused controversy. We consider the case where the Universe experiences…

Cosmology and Nongalactic Astrophysics · Physics 2024-10-03 Keisuke Inomata

It is known that the single-field inflation with a transient ultra-slow-roll phase can produce a large curvature perturbation at small scales for the formation of primordial black holes. In our previous work, we have considered quantum loop…

Cosmology and Nongalactic Astrophysics · Physics 2026-01-09 Shu-Lin Cheng , Da-Shin Lee , Kin-Wang Ng

We revisit one-loop corrections to the power spectrum of curvature perturbations $\zeta$ in an inflationary scenario containing a transient ultra-slow-roll (USR) period. In Ref.[1], it was argued that one-loop corrections to the power…

High Energy Physics - Theory · Physics 2024-12-17 Ryodai Kawaguchi , Shinji Tsujikawa , Yusuke Yamada

In order to produce appreciable amount of primordial black holes (PBHs), the square amplitude of curvature perturbation must take a large value of $\mathcal{O}(0.01)$, namely, seven digits larger than the value observed by cosmic microwave…

Cosmology and Nongalactic Astrophysics · Physics 2025-05-08 Jason Kristiano , Jun'ichi Yokoyama

We reconsider back-reaction from large amplitude, short-scale perturbations onto a long wavelength adiabatic mode. In a loop expansion of the long-mode power spectrum, this back-reaction appears first at 1-loop. Due to the separation…

Cosmology and Nongalactic Astrophysics · Physics 2026-01-21 Laura Iacconi , David Mulryne , David Seery

The one-loop corrections (1LC) to the power spectrum of scalar perturbations arising from cubic interactions in the single-field E-type $\alpha$-attractor models of inflation and primordial black hole (PBH) production are numerically…

General Relativity and Quantum Cosmology · Physics 2025-05-19 Daniel Frolovsky , Sergei V. Ketov

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

We estimate fermion loop corrections to the two-point correlation function of primordial tensor perturbations in a slow-roll inflationary background. We particularly compute an explicit term of one-loop correction from a massless fermion,…

High Energy Physics - Theory · Physics 2012-11-22 Kaixi Feng , Yi-Fu Cai , Yun-Song Piao
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