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We study the effect on the primordial cosmological perturbations of a sharp transition from inflationary to a radiation and matter dominated epoch respectively. We assume that the perturbations are generated by the vacuum fluctuations of a…

Cosmology and Nongalactic Astrophysics · Physics 2011-03-17 Ignacio Zaballa , Misao Sasaki

Although the paradigm of inflation has been extensively studied to demonstrate how macroscopic inhomogeneities in our universe originate from quantum fluctuations, most of the established literature ignores the crucial role that…

High Energy Physics - Theory · Physics 2022-11-30 Suddhasattwa Brahma , Arjun Berera , Jaime Calderón-Figueroa

The end of inflation is connected to the standard cosmological scenario through reheating. During reheating, the inflaton oscillates around the minimum of the potential and thus decays into the daughter particles that populate the Universe…

General Relativity and Quantum Cosmology · Physics 2016-10-19 R. Kabir , A. Mukherjee , D. Lohiya

Unifying the early-universe inflationary paradigm with late-time cosmic acceleration, while resolving the initial Big Bang singularity, remains one of the most profound challenges in modern cosmology. In this paper, we propose a…

General Relativity and Quantum Cosmology · Physics 2026-05-20 Zhiming Shuai , Xiangdong Zhang

This article discusses density perturbations in inflationary models, offering a pedagogical description of how these perturbations are generated by quantum fluctuations in the early universe. A key feature of inflation is that that rapid…

High Energy Physics - Theory · Physics 2014-01-15 Alan H. Guth

This thesis is dedicated to analysing the generation and destruction of quantum correlations in the context of inflationary cosmology and an experiment of 'analogue' preheating. Inflation is a phase of accelerated expansion of the Universe,…

General Relativity and Quantum Cosmology · Physics 2024-12-04 Amaury Micheli

The era of precision cosmology has allowed us to accurately determine many important cosmological parameters, in particular via the CMB. Confronting Loop Quantum Cosmology with these observations provides us with a powerful test of the…

General Relativity and Quantum Cosmology · Physics 2012-04-06 Ivan Agullo , Abhay Ashtekar , William Nelson

We investigate the quintessential inflation in the logarithmic Cartan $F(R)$ gravity. A small logarithmic modification of the general relativity has the potential to introduce both inflation and dark energy. We evaluate the time evolution…

High Energy Physics - Theory · Physics 2023-12-20 Tomohiro Inagaki , Masahiko Taniguchi

We consider inflation in a universe with a positive cosmological constant and a nonminimally coupled scalar field, in which the field couples both quadratically and quartically to the Ricci scalar. When considered in the Einstein frame and…

General Relativity and Quantum Cosmology · Physics 2015-08-21 Dražen Glavan , Anja Marunović , Tomislav Prokopec

We study oscillatory universes within the context of Loop Quantum Cosmology. We make a comparative study of flat and positively curved universes sourced by scalar fields with either positive or negative potentials. We investigate how…

General Relativity and Quantum Cosmology · Physics 2009-11-10 D. J. Mulryne , N. J. Nunes , R. Tavakol , J. E. Lidsey

The model of fresh inflation with increasing cosmological parameter provides sufficient e-folds to solve the flatness/horizon problem and the density fluctuations agree with experimental values. In this model the temperature increases…

High Energy Physics - Phenomenology · Physics 2009-11-10 Mauricio Bellini

We consider curved space quantum corrections to the equations of motion of the inflaton field in the early Universe. Using the stochastic formalism in phase space, we demonstrate that the quantum corrected evolution of the inflaton can…

High Energy Physics - Phenomenology · Physics 2009-09-25 Zygmunt Lalak , Rudolf Poppe

In this paper we study possible observational consequences of the bouncing cosmology. We consider a model where a phase of inflation is preceded by a cosmic bounce. While we consider in this paper only that the bounce is due to loop quantum…

General Relativity and Quantum Cosmology · Physics 2014-11-21 Jakub Mielczarek , Michal Kamionka , Aleksandra Kurek , Marek Szydlowski

We examine the dynamics of a closed cosmology whose matter source is that of a conformally coupled scalar field with a broken ${\rm SO}(1,1)$ symmetry, which correspond to the $\alpha$-attractors proposed by Linde and Kallosh. Following a…

General Relativity and Quantum Cosmology · Physics 2020-02-19 David Sloan , Konstantinos Dimopoulos , Sotirios Karamitsos

In this letter, we propose a model of inflationary cosmology with a bounce preceded and study its primordial curvature perturbations. Our model gives rise to a primordial power spectrum with a feature of oscillation on large scales compared…

Astrophysics · Physics 2009-02-02 Yi-Fu Cai , Tao-tao Qiu , Jun-Qing Xia , Xinmin Zhang

In this paper, we first provide a brief review of the effective dynamics of two recently well-studied models of modified loop quantum cosmologies (mLQCs), which arise from different regularizations of the Hamiltonian constraint and show the…

General Relativity and Quantum Cosmology · Physics 2021-06-25 Bao-Fei Li , Parampreet Singh , Anzhong Wang

In Loop Quantum Gravity mathematically rigorous models of full quantum gravity were proposed. In this paper we study a cosmological sector of one of the models describing quantum gravity with positive cosmological constant coupled to…

General Relativity and Quantum Cosmology · Physics 2022-11-09 Marcin Kisielowski

In this paper we investigate the cosmological dynamics of geometric inflation by means of the tools of the dynamical systems theory. We focus in the study of two explicit models where it is possible to sum the infinite series of higher…

General Relativity and Quantum Cosmology · Physics 2021-03-31 Israel Quiros , Roberto De Arcia , Ricardo García-Salcedo , Tame Gonzalez , Francisco X. Linares Cedeño , Ulises Nucamendi

I consider a quantum system that possesses key features of quantum shape dynamics and show that the evolution of wave-packets will become increasingly classical at late times and tend to evolve more and more like an expanding classical…

General Relativity and Quantum Cosmology · Physics 2014-04-21 Tim A. Koslowski

In this article we explore the pre-inflationary background dynamics of an FLRW universe sourced by a scalar field with monodromy potential in LQC framework. In particular we calculate the number of e-folds, $N_{inf}$, produced during the…

General Relativity and Quantum Cosmology · Physics 2018-11-15 Manabendra Sharma , M. Shahalam , Wu Qiang , Anzhong Wang