Bounce Cosmology

A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "Cosmology".

Deadline for manuscript submissions: closed (28 February 2021) | Viewed by 14115

Special Issue Editors

Department of Astronomy, School of Physical Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei 230026, China
Interests: bounce cosmology; inflation; dark energy; curvaton; curvature perturbation; primordial gravitational waves; cosmic microwave background; modified gravity; black holes; cosmic strings; cosmological perturbations
Special Issues, Collections and Topics in MDPI journals
Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, 30-348 Krakow, Poland
Interests: mathematical physics; elementary particle physics; theoretical physics
Center for Field Theory and Particle Physics and Department of Physics, Fudan University, Shanghai 200433, China
Interests: early cosmology; inflation; dark energy; quantum comsology and quantum gravity; quantum gravity phenomenology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Research on cosmology has been greatly developed over the past few decades, from both observational and theoretical points of view. Particularly, with the help of a series of cosmic microwave background observations, we are fortunate to be able to witness the golden age that the probe of the earliest moments of our Universe has become possible. The paradigm of inflationary cosmology, which was proposed in previous decades, was applied to understand the initial conditions issued in the hot big bang cosmology, and soon became the most prevailing theory describing the early universe. It is interesting to note that, however, that inflationary cosmology is not a unique paradigm describing the early universe. Moreover, general inflation models have difficulty in explaining the existence of the space-time singularity at the very moment that the universe was born. Bearing recent experimental developments and theoretical challenges in mind, many new proposals have been put forward by cosmologists for the theory of the early universe, beyond the paradigm of inflationary LCDM cosmology. Namely, there is a “pre big bang” scenario, the “ekpyrotic/cyclic universe” configuration, the reputed paradigm of the emergent universe, and from the perspective of phenomenological considerations, string gas cosmology, as well as the matter bounce scenario.

In the research field of bounce cosmology, together with the possible resolutions to the big bang singularity, a remarkable amount of progress has been made by cosmologists in the past decade. In light of recent extensive developments, the Universe Editorial Board has invited a number of major experts in this field to contribute to this Special Issue on theoretical developments as well as underlying challenges, related to bounce cosmology, and, mostly important, to explore the direction of cosmological study upon the big bang singularity in the future.

It is our great pleasure to serve as the Guest Editors of this Special Issue on “Bounce Cosmology”. We are very grateful to all authors who have contributed relevant research and the compiling of review articles. We expect that this Special Issue will shed light on developments regarding theoretical and observational cosmology in the near future. Finally, we thank assistant editors for their valuable contributions for the editorial work as well as the Universe for the publication of this issue.

Sincerely,

Prof. Dr. Yi-Fu Cai
Dr. Chunshan Lin
Prof. Dr. Antonino Marciano
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Universe is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) is waived for well-prepared manuscripts submitted to this issue. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (5 papers)

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Research

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17 pages, 520 KiB  
Article
Stability of a Viable Non-Minimal Bounce
by Debottam Nandi
Universe 2021, 7(3), 62; https://0-doi-org.brum.beds.ac.uk/10.3390/universe7030062 - 10 Mar 2021
Cited by 8 | Viewed by 1385
Abstract
The main difficulties in constructing a viable early Universe bouncing model are: to bypass the observational and theoretical no-go theorem, to construct a stable non-singular bouncing phase, and perhaps, the major concern of it is to construct a stable attractor solution which can [...] Read more.
The main difficulties in constructing a viable early Universe bouncing model are: to bypass the observational and theoretical no-go theorem, to construct a stable non-singular bouncing phase, and perhaps, the major concern of it is to construct a stable attractor solution which can evade the Belinsky–Khalatnikov–Lifshitz (BKL) instability as well. In this article, in the homogeneous and isotropic background, we extensively study the stability analysis of the recently proposed viable non-minimal bouncing theory in the presence of an additional barotropic fluid and show that, the bouncing solution remains stable and can evade BKL instability for a wide range of the model parameter. We provide the expressions that explain the behavior of the Universe in the vicinity of the required fixed point i.e., the bouncing solution and compare our results with the minimal theory and show that ekpyrosis is the most stable solution in any scenario. Full article
(This article belongs to the Special Issue Bounce Cosmology)
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17 pages, 399 KiB  
Article
Bounce Cosmology in Generalized Modified Gravities
by Georgios Minas, Emmanuel N. Saridakis, Panayiotis C. Stavrinos and Alkiviadis Triantafyllopoulos
Universe 2019, 5(3), 74; https://0-doi-org.brum.beds.ac.uk/10.3390/universe5030074 - 10 Mar 2019
Cited by 30 | Viewed by 3191
Abstract
We investigate the bounce realization in the framework of generalized modified gravities arising from Finsler and Finsler-like geometries. In particular, a richer intrinsic geometrical structure is reflected in the appearance of extra degrees of freedom in the Friedmann equations that can drive the [...] Read more.
We investigate the bounce realization in the framework of generalized modified gravities arising from Finsler and Finsler-like geometries. In particular, a richer intrinsic geometrical structure is reflected in the appearance of extra degrees of freedom in the Friedmann equations that can drive the bounce. We examine various Finsler and Finsler-like constructions. In the cases of general very special relativity, as well as of Finsler-like gravity on the tangent bundle, we show that a bounce cannot easily be obtained. However, in the Finsler–Randers space, induced scalar anisotropy can fulfil bounce conditions, and bouncing solutions are easily obtained. Finally, for the general class of theories that include a nonlinear connection, a new scalar field is induced, leading to a scalar–tensor structure that can easily drive a bounce. These features reveal the capabilities of Finsler and Finsler-like geometries. Full article
(This article belongs to the Special Issue Bounce Cosmology)
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6 pages, 203 KiB  
Article
Pre-Big-Bang Black-Hole Remnants and Past Low Entropy
by Carlo Rovelli and Francesca Vidotto
Universe 2018, 4(11), 129; https://0-doi-org.brum.beds.ac.uk/10.3390/universe4110129 - 18 Nov 2018
Cited by 10 | Viewed by 3341
Abstract
Dark matter could be composed by black-hole remnants formed before the big-bang era in a bouncing cosmology. This hypothetical scenario has implications on the issue of the arrow of time: it upsets a common attribution of past low entropy to the state of [...] Read more.
Dark matter could be composed by black-hole remnants formed before the big-bang era in a bouncing cosmology. This hypothetical scenario has implications on the issue of the arrow of time: it upsets a common attribution of past low entropy to the state of the geometry and suggests a possible realisation of the perspectival interpretation of past low entropy. Full article
(This article belongs to the Special Issue Bounce Cosmology)
25 pages, 773 KiB  
Article
Cosmological Bounce and Some Other Solutions in Exponential Gravity
by Pritha Bari, Kaushik Bhattacharya and Saikat Chakraborty
Universe 2018, 4(10), 105; https://0-doi-org.brum.beds.ac.uk/10.3390/universe4100105 - 12 Oct 2018
Cited by 11 | Viewed by 2547
Abstract
In this work, we present some cosmologically relevant solutions using the spatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime in metric f ( R ) gravity where the form of the gravitational Lagrangian is given by 1 α e α R . In the low curvature [...] Read more.
In this work, we present some cosmologically relevant solutions using the spatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime in metric f ( R ) gravity where the form of the gravitational Lagrangian is given by 1 α e α R . In the low curvature limit this theory reduces to ordinary Einstein-Hilbert Lagrangian together with a cosmological constant term. Precisely because of this cosmological constant term this theory of gravity is able to support nonsingular bouncing solutions in both matter and vacuum background. Since for this theory of gravity f and f is always positive, this is free of both ghost instability and tachyonic instability. Moreover, because of the existence of the cosmological constant term, this gravity theory also admits a de-Sitter solution. Lastly we hint towards the possibility of a new type of cosmological solution that is possible only in higher derivative theories of gravity like this one. Full article
(This article belongs to the Special Issue Bounce Cosmology)
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Review

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46 pages, 1135 KiB  
Review
Bouncing Quantum Cosmology
by Nelson Pinto-Neto
Universe 2021, 7(4), 110; https://0-doi-org.brum.beds.ac.uk/10.3390/universe7040110 - 20 Apr 2021
Cited by 10 | Viewed by 1908
Abstract
The goal of this contribution is to present the properties of a class of quantum bouncing models in which the quantum bounce originates from the Dirac canonical quantization of a midi-superspace model composed of a homogeneous and isotropic background, together with small inhomogeneous [...] Read more.
The goal of this contribution is to present the properties of a class of quantum bouncing models in which the quantum bounce originates from the Dirac canonical quantization of a midi-superspace model composed of a homogeneous and isotropic background, together with small inhomogeneous perturbations. The resulting Wheeler-DeWitt equation is interpreted in the framework of the de Broglie-Bohm quantum theory, enormously simplifying the calculations, conceptually and technically. It is shown that the resulting models are stable and they never get to close to the Planck energy, where another more involved quantization scheme would have to be evoked, and they are compatible with present observations. Some physical effects around the bounce are discussed, like baryogenesis and magnetogenesis, and the crucial role of dark matter and dark energy is also studied. Full article
(This article belongs to the Special Issue Bounce Cosmology)
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