Bouncing Cosmology and the Early Universe: From Theory to Observations

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

Deadline for manuscript submissions: 30 September 2025 | Viewed by 757

Special Issue Editor


E-Mail Website
Guest Editor
Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
Interests: particle physics; high-energy physics; high-energy physics theory; theoretical high-energy physics; astroparticle physics; fundamental physics; theoretical particle physics; field theory
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Bouncing cosmology offers an alternative to the Big Bang by positing cyclic phases of contraction and expansion, avoiding singularities. Theoretical advances, such as loop quantum cosmology and \(f(R)\) gravity, provide mechanisms for a smooth bounce via quantum corrections and higher-order modifications. Ekpyrotic models using scalar fields address issues such as anisotropy, enhancing the plausibility of these scenarios.

Observations from the CMB and large-scale structure constrain bouncing cosmologies. Features such as suppressed power at large scales and specific non-Gaussian patterns could distinguish these models from inflationary paradigms. Data from Planck and BICEP/Keck collaborations already support aspects of certain bounce models. Upcoming missions, such as LiteBIRD, aim to refine these constraints further, testing the models' predictions against inflation.

Bouncing cosmology also connects with broader early-universe phenomena. Mechanisms for pre-bounce baryogenesis offer solutions to the matter–antimatter asymmetry. Links between bouncing models and late-time observations, such as cosmic acceleration and primordial string remnants, suggest a potential to address dark energy and dark matter within this framework. These developments demonstrate the potential of bouncing cosmology as a compelling alternative framework for understanding the universe’s origins.

Dr. Arnab Dasgupta
Guest Editor

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 submissions that pass pre-check are 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. 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.

Keywords

  • bouncing cosmology
  • cyclic universe
  • cosmic microwave background (CMB)
  • matter–antimatter asymmetry
  • dark energy and dark matter

Benefits of Publishing in a Special Issue

  • Ease of navigation: Grouping papers by topic helps scholars navigate broad scope journals more efficiently.
  • Greater discoverability: Special Issues support the reach and impact of scientific research. Articles in Special Issues are more discoverable and cited more frequently.
  • Expansion of research network: Special Issues facilitate connections among authors, fostering scientific collaborations.
  • External promotion: Articles in Special Issues are often promoted through the journal's social media, increasing their visibility.
  • Reprint: MDPI Books provides the opportunity to republish successful Special Issues in book format, both online and in print.

Further information on MDPI's Special Issue policies can be found here.

Published Papers (1 paper)

Order results
Result details
Select all
Export citation of selected articles as:

Research

14 pages, 933 KiB  
Article
Evolution of the Early Universe in Einstein–Cartan Theory
by Qihong Huang, He Huang, Bing Xu and Kaituo Zhang
Universe 2025, 11(5), 147; https://doi.org/10.3390/universe11050147 - 2 May 2025
Viewed by 485
Abstract
Einstein–Cartan theory is a generalization of general relativity that introduces spacetime torsion. In this paper, we perform phase space analysis to investigate the evolution of the early universe in Einstein–Cartan theory. By studying the stability of critical points in the dynamical system, we [...] Read more.
Einstein–Cartan theory is a generalization of general relativity that introduces spacetime torsion. In this paper, we perform phase space analysis to investigate the evolution of the early universe in Einstein–Cartan theory. By studying the stability of critical points in the dynamical system, we find that there exist two stable critical points which represent an Einstein static solution and an expanding solution, respectively. After analyzing the phase diagram of the dynamical system, we find that the early universe may exhibit an Einstein static state, an oscillating state, or a bouncing state. By assuming the equation of state ω can decrease over time t, the universe can depart from the initial Einstein static state, oscillating state, or bouncing state and then evolve into an inflationary phase. Then, we analyze four different inflationary evolution cases in Einstein–Cartan theory and find that a time-variable equation of state ω cannot yield values of ns and r consistent with observations, while a time-invariant equation of state ω is supported by the Planck 2018 results. Thus, in Einstein–Cartan theory, the universe likely originates from a bouncing state rather than an Einstein static state or an oscillating state. Full article
Show Figures

Figure 1

Back to TopTop