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Universe
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Probing the Early Universe
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Probing the Early Universe

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

Deadline for manuscript submissions: 31 May 2025 | Viewed by 3696

Special Issue Editor

Prof. Dr. Øyvind Grøn

E-Mail Website
Guest Editor
Faculty of Technology, Art and Design, College of Applied Sciences, Oslo and Akershus University, St. Olavs Plass, P.O. Box 4, NO-0130 Oslo, Norway
Interests: cosmology; early universe; inflation; general theory of relativity; electromagnetism of uniformly accelerated charges; conceptual understanding of general relativity
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We will here give a wide definition of the concept “Early Universe”. Therefore, we will include not only the first moments, such as the inflationary era lasting about 10-33 s, the time when the asymmetry between matter and antimatter appeared, the first ten minutes with cosmic nucleosynthesis, and the time about 380,000 years later when the universe became transparent for the radiation which now makes up the cosmic microwave background, but also the time afterward up to one billion years after the inflationary era, when the first stars and galaxies appeared, and the reionization of the cosmic matter happened. New observational results obtained for example by means of the James Webb Telescope are welcome. We want to invite you to contribute a scientific article with new results or a review article to this Special Issue.

Prof. Dr. Øyvind Grøn
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

  • the Planck era (t < 10-43 s)
  • grand unification era (t < 10-36 s)
  • the inflationary era (t < 10-33 s)
  • electroweak epoch (10-33 s < t < 10-12 s)
  • quark era (10-12 s < t < 10-5 s)
  • hadron era (10-5 s < t < 1 s)
  • lepton era with neutrino decoupling (1 s < t < 10 s)
  • cosmic nucleosynthesis (10 s < t < 1000 s)
  • radiation dominated and ‘foggy’ era (1000 s < t < 380,000 years)
  • recombination (18,000 years < t < 380,000 years)
  • the dark era (380,000 years < t < 150 million years)
  • first stars and galaxies (200 to 400 million years)
  • cosmic reionization (200 million to 1 billion years)

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Published Papers (3 papers)

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Research

24 pages, 774 KiB  
Article
An Infinitely Old Universe with Planck Fields Before and After the Big Bang
by Dragana Pilipović
Universe 2024, 10(10), 400; https://doi.org/10.3390/universe10100400 - 17 Oct 2024
Viewed by 1259
Abstract
The Robertson–Walker minimum length (RWML) theory considers stochastically perturbed spacetime to describe an expanding universe governed by geometry and diffusion. We explore the possibility of static, torsionless universe eras with conserved energy density. We find that the RWML theory provides asymptotically static equations [...] Read more.
The Robertson–Walker minimum length (RWML) theory considers stochastically perturbed spacetime to describe an expanding universe governed by geometry and diffusion. We explore the possibility of static, torsionless universe eras with conserved energy density. We find that the RWML theory provides asymptotically static equations of state under positive curvature both far in the past and far into the future, with a Big Bang singularity in between. Full article
(This article belongs to the Special Issue Probing the Early Universe)
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29 pages, 5836 KiB  
Article
Calibration Error in 21-Centimeter Global Spectrum Experiment
by Shijie Sun, Eloy de Lera Acedo, Fengquan Wu, Bin Yue, Jiacong Zhu and Xuelei Chen
Universe 2024, 10(6), 236; https://doi.org/10.3390/universe10060236 - 27 May 2024
Cited by 2 | Viewed by 1051
Abstract
The redshifted 21 cm line signal is a powerful probe of the cosmic dawn and the epoch of reionization. The global spectrum can potentially be detected with a single antenna and spectrometer. However, this measurement requires an extremely accurate calibration of the instrument [...] Read more.
The redshifted 21 cm line signal is a powerful probe of the cosmic dawn and the epoch of reionization. The global spectrum can potentially be detected with a single antenna and spectrometer. However, this measurement requires an extremely accurate calibration of the instrument to facilitate the separation of the 21 cm signal from the much brighter foregrounds and possible variations in the instrument response. Understanding how the measurement errors propagate in a realistic instrument system and affect system calibration is the focus of this work. We simulate a 21 cm global spectrum observation based on the noise wave calibration scheme. We focus on how measurement errors in reflection coefficients affect the noise temperature and how typical errors impact the recovery of the 21 cm signal, especially in the frequency domain. Results show that for our example set up, a typical vector network analyzer (VNA) measurement error in the magnitude of the reflection coefficients of the antenna, receiver, and open cable, which are 0.001, 0.001, and 0.002 (linear), respectively, would result in a 200 mK deviation on the detected signal, and a typical measurement error of 0.48°, 0.78°, or 0.15° in the respective phases would cause a 40 mK deviation. The VNA measurement error can greatly affect the result of a 21 cm global spectrum experiment using this calibration technique, and such a feature could be mistaken for or be combined with the 21 cm signal. Full article
(This article belongs to the Special Issue Probing the Early Universe)
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23 pages, 603 KiB  
Article
PeV-Scale SUSY and Cosmic Strings from F-Term Hybrid Inflation
by Constantinos Pallis
Universe 2024, 10(5), 211; https://doi.org/10.3390/universe10050211 - 8 May 2024
Cited by 10 | Viewed by 837
Abstract
We consider F-term hybrid inflation (FHI) and SUSY breaking in the context of a B−L extension of the MSSM that largely respects a global U(1)R symmetry. The hidden sector Kaehler manifold enjoys an enhanced [...] Read more.
We consider F-term hybrid inflation (FHI) and SUSY breaking in the context of a B−L extension of the MSSM that largely respects a global U(1)R symmetry. The hidden sector Kaehler manifold enjoys an enhanced SU(1,1)/U(1) symmetry, with the scalar curvature determined by the achievement of a SUSY-breaking de Sitter vacuum without undesirable tuning. FHI turns out to be consistent with the data, provided that the magnitude of the emergent soft tadpole term is confined to the range (1.2–100) TeV, and it is accompanied by the production of B−L cosmic strings. If these are metastable, they are consistent with the present observations from PTA experiments on the stochastic background of gravitational waves with dimensionless tension Gμcs≃(1−9.2)·10−8. The μ parameter of the MSSM arises by appropriately adapting the Giudice–Masiero mechanism and facilitates the out-of-equilibrium decay of the R saxion at a reheat temperature lower than about 71 GeV. Due to the prolonged matter-dominated era, the gravitational wave signal is suppressed at high frequencies. The SUSY mass scale turns out to lie in the PeV region. Full article
(This article belongs to the Special Issue Probing the Early Universe)
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