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Universe
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Dark Energy and Dark Matter
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Dark Energy and Dark Matter

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

Deadline for manuscript submissions: 16 May 2025 | Viewed by 6248

Special Issue Editor

Prof. Dr. Yan Gong

E-Mail Website
Guest Editor
National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China
Interests: dark energy; dark matter; large-scale structure; epoch of reionization; cosmic infrared background

Special Issue Information

Dear Colleagues,

Dark energy and dark matter are of immense importance in current astronomy and physics research. Understanding their nature is of great significance when studying the origin, evolution, and ultimate fate of our Universe, and will promote the development of fundamental physics. Currently, various theoretical models of dark energy and dark matter have been proposed; various cosmological probes or means are used to test these models, such as Type Ia supernova (SN Ia), baryon acoustic oscillations (BAO), cosmic microwave background (CMB), gravitational lensing, galaxy clustering, cosmic void, intensity mapping, direct or indirect detection, etc. In addition, a series of next-generation ground- and space-based cosmological surveys will be launched over the next few years. The next decade is anticipated to be a golden age for cosmological studies, especially in relation to dark energy and dark matter.

This Special Issue aims to collect the latest studies on dark energy, dark matter, and modified gravity, including theories and observational results. Original research studies in the form of letters and articles are welcome. Predictions of future projects or new detection methods are also encouraged.

Prof. Dr. Yan Gong
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

  • dark energy
  • dark matter
  • modified gravity
  • theoretical model
  • cosmic acceleration
  • cosmic large-scale structure
  • gravitational lensing
  • galaxy clustering
  • intensity mapping
  • cosmological constraint

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Published Papers (6 papers)

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Research

Jump to: Review

11 pages, 278 KiB  
Article
The Variation of G and Λ in Cosmology
by Aroonkumar Beesham
Universe 2024, 10(11), 404; https://doi.org/10.3390/universe10110404 - 23 Oct 2024
Viewed by 565
Abstract
The idea of varying constants of nature is very old, and has commanded a lot of attention since first mooted. The variation in the gravitational parameter G and cosmological parameter Λ is still an active area of research. Since the idea of a [...] Read more.
The idea of varying constants of nature is very old, and has commanded a lot of attention since first mooted. The variation in the gravitational parameter G and cosmological parameter Λ is still an active area of research. Since the idea of a varying G was introduced by Dirac almost a century ago, there are even theories that have variable G such as the Brans–Dicke theory and the scale covariant theory. Both these theories also have a varying Λ in their full generalisations. A varying Λ was also introduced around the same time as that of varying G. It is interesting to note that a possible solution to the cosmological constant problem can be realised from a dynamic Λ. In this work, we focus on a varying Λ and G framework. In almost all studies in the simplest framework of variables Λ and G, it is found that one of them has to increase with time. However, observations and theoretical considerations indicate that both Λ and G should decrease with time. In this paper, we propose a solution to this problem, finding theories in which both Λ and G decrease with time. Full article
(This article belongs to the Special Issue Dark Energy and Dark Matter)
12 pages, 835 KiB  
Article
Primordial Axion Stars and Galaxy Halo Formation
by Alexander I. Nesterov
Universe 2024, 10(9), 369; https://doi.org/10.3390/universe10090369 - 12 Sep 2024
Viewed by 510
Abstract
Primordial axion stars, hypothetical stars formed from axions, could play an essential role in forming galaxy halos. These stars could have originated in the early universe shortly after the Big Bang. We show that the ultralight axions forming primordial stars can act as [...] Read more.
Primordial axion stars, hypothetical stars formed from axions, could play an essential role in forming galaxy halos. These stars could have originated in the early universe shortly after the Big Bang. We show that the ultralight axions forming primordial stars can act as the initial seeds for galaxy halos. Full article
(This article belongs to the Special Issue Dark Energy and Dark Matter)
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24 pages, 1325 KiB  
Article
Non-Canonical Dark Energy Parameter Evolution in a Canonical Quintessence Cosmology
by Rodger I. Thompson
Universe 2024, 10(9), 356; https://doi.org/10.3390/universe10090356 - 5 Sep 2024
Viewed by 517
Abstract
This study considers the specific case of a flat, minimally coupled to gravity, quintessence cosmology with a dark energy quartic polynomial potential that has the same mathematical form as the Higgs potential. Previous work on this case determined that the scalar field is [...] Read more.
This study considers the specific case of a flat, minimally coupled to gravity, quintessence cosmology with a dark energy quartic polynomial potential that has the same mathematical form as the Higgs potential. Previous work on this case determined that the scalar field is given by a simple expression of the Lambert W function in terms of the easily observable scale factor. This expression provides analytic equations for the evolution of cosmological dark energy parameters as a function of the scale factor for all points on the Lambert W function principal branch. The Lambert W function is zero at a scale factor of zero that marks the big bang. The evolutionary equations beyond the big bang describe a canonical universe that is similar to ΛCDM, making it an excellent dynamical template to compare with observational data. The portion of the W function principal before the big bang extends to the infinite pre-bang past. It describes a noncanonical universe with an initially very low mass density that contracts by rolling down the dark energy potential to a singularity, big bang, at the scale factor zero point. This provides a natural origin for the big bang. It also raises the possibility that the universe existed before the big bang and is far older, and that it was once far larger than its current size. The recent increasing interest in the possibility of a dynamical universe instead of ΛCDM makes the exploration of the nature of such universes particularly relevant. Full article
(This article belongs to the Special Issue Dark Energy and Dark Matter)
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21 pages, 2528 KiB  
Article
On Dark Matter and Dark Energy in CCC+TL Cosmology
by Rajendra P. Gupta
Universe 2024, 10(6), 266; https://doi.org/10.3390/universe10060266 - 18 Jun 2024
Cited by 1 | Viewed by 1220
Abstract
Relaxing the temporal constancy constraint on coupling constants in an expanding universe results in Friedmann equations containing terms that may be interpreted as dark energy and dark matter. When tired light (TL) was considered to complement the redshift due to the expanding universe, [...] Read more.
Relaxing the temporal constancy constraint on coupling constants in an expanding universe results in Friedmann equations containing terms that may be interpreted as dark energy and dark matter. When tired light (TL) was considered to complement the redshift due to the expanding universe, the resulting covarying coupling constants (CCC+TL) model not only fit the Type Ia supernovae data as precisely as the ΛCDM model, but also resolved concerns about the angular size of cosmic dawn galaxies observed by the James Webb Space Telescope. The model was recently shown to be compliant with the baryon acoustic oscillation features in the galaxy distribution and the cosmic microwave background (CMB). This paper demonstrates that dark energy and dark matter of the standard ΛCDM model are not arbitrary but can be derived from the CCC approach based on Dirac’s 1937 hypothesis. The energy densities associated with dark matter and dark energy turn out to be about the same in the ΛCDM and the CCC+TL models. However, the critical density in the new model can only account for the baryonic matter in the universe, raising concerns about how to account for observations requiring dark matter. We therefore analyze some key parameters of structure formation and show how they are affected in the absence of dark matter in the CCC+TL scenario. It requires reconsidering alternatives to dark matter to explain observations on gravitationally bound structures. Incidentally, since the CCC models inherently have no dark energy, it has no coincidence problem. The model’s consistency with the CMB power spectrum, BBN element abundances, and other critical observations is yet to be established. Full article
(This article belongs to the Special Issue Dark Energy and Dark Matter)
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27 pages, 4227 KiB  
Article
A Search for Magnetized Quark Nuggets (MQNs), a Candidate for Dark Matter, Accumulating in Iron Ore
by J. Pace VanDevender, T. Sloan and Michael Glissman
Universe 2024, 10(1), 27; https://doi.org/10.3390/universe10010027 - 9 Jan 2024
Cited by 1 | Viewed by 1675
Abstract
A search has been carried out for Magnetized Quark Nuggets (MQNs) accumulating in iron ore over geologic time. MQNs, which are theoretically consistent with the Standard Models of Physics and of Cosmology, have been suggested as dark-matter candidates. Indirect evidence of MQNs has [...] Read more.
A search has been carried out for Magnetized Quark Nuggets (MQNs) accumulating in iron ore over geologic time. MQNs, which are theoretically consistent with the Standard Models of Physics and of Cosmology, have been suggested as dark-matter candidates. Indirect evidence of MQNs has been previously inferred from observations of magnetars and of non-meteorite impact craters. It is shown in this paper that MQNs can accumulate in taconite (iron ore) and be transferred into ferromagnetic rod-mill liners during processing of the ore. When the liners are recycled to make fresh steel, they are heated to higher than the Curie temperature so that their ferromagnetic properties are destroyed. The MQNs would then be released and fall into the ferromagnetic furnace bottom where they would be trapped. Three such furnace bottoms have been magnetically scanned to search for the magnetic anomalies consistent with trapped MQNs. The observed magnetic anomalies are equivalent to an accumulation rate of ~1 kg of MQNs per 1.2 × 108 kg of taconite ore processed. The results are consistent with MQNs but there could be other, unknown explanations. We propose an experiment and calculations to definitively test the MQN hypothesis for dark matter. Full article
(This article belongs to the Special Issue Dark Energy and Dark Matter)
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Review

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41 pages, 1918 KiB  
Review
Semi-Symmetric Metric Gravity: A Brief Overview
by Himanshu Chaudhary, Lehel Csillag and Tiberiu Harko
Universe 2024, 10(11), 419; https://doi.org/10.3390/universe10110419 - 7 Nov 2024
Viewed by 528
Abstract
We present a review of the Semi-Symmetric Metric Gravity (SSMG) theory, representing a geometric extension of standard general relativity, based on a connection introduced by Friedmann and Schouten in 1924. The semi-symmetric connection is a connection that generalizes the Levi-Civita one by allowing [...] Read more.
We present a review of the Semi-Symmetric Metric Gravity (SSMG) theory, representing a geometric extension of standard general relativity, based on a connection introduced by Friedmann and Schouten in 1924. The semi-symmetric connection is a connection that generalizes the Levi-Civita one by allowing for the presence of a simple form of the torsion, described in terms of a torsion vector. The Einstein field equations are postulated to have the same form as in standard general relativity, thus relating the Einstein tensor constructed with the help of the semi-symmetric connection, with the energy–momentum tensor tensor. The inclusion of the torsion contributions in the field equations has intriguing cosmological implications, particularly during the late-time evolution of the Universe. Presumably, these effects also dominate under high-energy conditions, and thus SSMG could potentially address unresolved issues in general relativity and cosmology, such as the initial singularity, inflation, or the 7Li problem of the Big-Bang Nucleosynthesis. The explicit presence of torsion in the field equations leads to the non-conservation of the energy–momentum tensor tensor, which can be interpreted within the irreversible thermodynamics of open systems as describing particle creation processes. We also review in detail the cosmological applications of the theory, and investigate the statistical tests for several models, by constraining the model parameters via comparison with several observational datasets. Full article
(This article belongs to the Special Issue Dark Energy and Dark Matter)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Elucidating the Dark Energy and Dark Matter Phenomena within the Scale Invariant Vacuum (SIV) Paradigm
Authors: Vesselin G. Gueorguiev; Andre Maeder
Affiliation: 1. Ronin Institute, Montclair, United States; 2. Faculty of Science, Geneva, Switzerland
Abstract: The phenomenon of Dark Energy (DE) is generally viewed as a place holder for the energy that drives the accelerated expansion of the Universe. The non-zero Einstein Cosmological Constant Λ_E is one possible manifestation of such DE as a constant energy density of the vacuum that does not seem to gravitate. Here we interpret the non-zero Cosmological Constant via the idea of scale invariant cosmology. We re-derive the relevant scale factor λ and its defining equations within the Scale Invariant Vacuum (SIV) paradigm; then, we address the problem of the missing mass in galactic and extra galactic scales by deriving a MOND-like relation g ∼ \sqrt{a0 gN} within the SIV paradigm. The corresponding values for Λ_E and the MOND fundamental acceleration a0 are shown to be at the correct order of magnitude as observed, that is, a0 ≈ 10^(−10)m/s^2 and Λ_E≈ 1.8 × 10^{-52} m^(-2). A new early dark energy term Tμν ∼ κ H within SIV is introduced that could be relevant for the resolution of the Hubble tension.

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