Origins and Natures of Inflation, Dark Matter and Dark Energy, 2nd Edition

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

Deadline for manuscript submissions: 30 June 2025 | Viewed by 6052

Special Issue Editor

Special Issue Information

Dear Colleagues,

Exploring the origins of inflation, dark matter, and dark energy is one of the most important problems in modern physics and cosmology. It is strongly expected that primordial gravitational waves will be detected in the near future, revealing the energy scale of inflation of the early universe.

Regarding the origin of dark matter, there are two main possibilities: The first is new particles in particle theory models beyond the standard model. The second is astrophysical objects. On the other hand, two representative approaches exist to investigate the properties of dark energy components leading to late-time cosmic acceleration. One is the introduction of unknown matter, called dark energy, with the negative pressure in general relativity. The other is the extension of gravity on large scales, known as geometrical dark energy.

The main subject of this Special Issue is to understand the origins and true nature of inflation, dark matter, and dark energy. We can consider not only phenomenological approaches but also more fundamental physics, such as higher-dimensional gravity theories, quantum gravity, quantum cosmology, physics in the early universe, quantum field theories and gauge field theories in curved spacetime, string theories, brane world models, and the holographic principle. It is our pleasure to invite submissions to this Special Issue on inflation, dark matter, dark energy, and related foundations of physics.

Dr. Kazuharu Bamba
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

  • inflation
  • dark matter
  • dark energy
  • alternative theory of gravity
  • cosmology
  • physics in the early universe
  • cosmological perturbation theory
  • cosmic microwave background radiation
  • gravitational waves
  • large-scale structure of the universe

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.
  • e-Book format: Special Issues with more than 10 articles can be published as dedicated e-books, ensuring wide and rapid dissemination.

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

Published Papers (8 papers)

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

Research

15 pages, 412 KiB  
Article
Gauss–Bonnet-Induced Symmetry Breaking/Restoration During Inflation
by Yermek Aldabergenov and Daulet Berkimbayev
Universe 2025, 11(3), 98; https://doi.org/10.3390/universe11030098 - 17 Mar 2025
Viewed by 206
Abstract
We propose a mechanism for symmetry breaking or restoration that can occur in the middle of inflation, due to the coupling of the Gauss–Bonnet term to a charged scalar. The Gauss–Bonnet coupling results in an inflaton-dependent effective squared mass of the charged scalar, [...] Read more.
We propose a mechanism for symmetry breaking or restoration that can occur in the middle of inflation, due to the coupling of the Gauss–Bonnet term to a charged scalar. The Gauss–Bonnet coupling results in an inflaton-dependent effective squared mass of the charged scalar, which can change its sign (around the symmetric point) during inflation. This can lead to spontaneous breaking of the symmetry, or to its restoration, if it is initially broken. We show the conditions under which the backreaction of the Gauss–Bonnet coupling on the inflationary background is negligible, such that the predictions of a given inflationary model are unaffected by the symmetry breaking/restoration process. Full article
Show Figures

Figure 1

40 pages, 1110 KiB  
Article
Time Scales of Slow-Roll Inflation in Asymptotically Safe Cosmology
by József Nagy, Sándor Nagy and Kornél Sailer
Universe 2025, 11(3), 77; https://doi.org/10.3390/universe11030077 - 21 Feb 2025
Viewed by 189
Abstract
Making use of the well-known renormalization group (RG) scale dependences of the gravitational couplings in the framework of the two-parameter Einstein–Hilbert (EH) theory of gravity, the single scalar field-driven cosmological inflation is discussed in a spatially homogeneous, isotropic, and flat model universe. The [...] Read more.
Making use of the well-known renormalization group (RG) scale dependences of the gravitational couplings in the framework of the two-parameter Einstein–Hilbert (EH) theory of gravity, the single scalar field-driven cosmological inflation is discussed in a spatially homogeneous, isotropic, and flat model universe. The inflaton field is represented by a one-component real, non-self-interacting, massive scalar field minimally coupled to gravity. Cases without and with the incorporation of the RG scaling of the inflaton mass are compared with each other and with the corresponding classical case. It is shown that the quantum improvement drastically alters the timing of the slow-roll inflation with the desirable number N,60 e-foldings, as compared with the classical case. Furthermore, accounting for the RG flow of the inflaton mass has an enormous effect on the timing of the desirable slow roll, too. Although providing the desirable slow-roll inflation, none of the versions of the investigated quantum-improved toy models provide a realistic value of the amplitude of the scalar perturbations. Full article
Show Figures

Figure 1

43 pages, 1224 KiB  
Article
Regularized Stress Tensor of Vector Fields in de Sitter Space
by Yang Zhang and Xuan Ye
Universe 2025, 11(2), 72; https://doi.org/10.3390/universe11020072 - 18 Feb 2025
Viewed by 274
Abstract
We study the Stueckelberg field in de Sitter space, which is a massive vector field with the gauge fixing (GF) term 12ζ(Aμ;μ)2. We obtain the vacuum stress tensor, which consists of the transverse, [...] Read more.
We study the Stueckelberg field in de Sitter space, which is a massive vector field with the gauge fixing (GF) term 12ζ(Aμ;μ)2. We obtain the vacuum stress tensor, which consists of the transverse, longitudinal, temporal, and GF parts, and each contains various UV divergences. By the minimal subtraction rule, we regularize each part of the stress tensor to its pertinent adiabatic order. The transverse stress tensor is regularized to the 0th adiabatic order, while the longitudinal, temporal, and GF stress tensors are regularized to the 2nd adiabatic order. The resulting total regularized vacuum stress tensor is convergent and maximally symmetric, has a positive energy density, and respects the covariant conservation, and thus, it can be identified as the cosmological constant that drives the de Sitter inflation. Under the Lorenz condition Aμ;μ=0, the regularized Stueckelberg stress tensor reduces to the regularized Proca stress tensor that contains only the transverse and longitudinal modes. In the massless limit, the regularized Stueckelberg stress tensor becomes zero, and is the same as that of the Maxwell field with the GF term, and no trace anomaly exists. If the order of adiabatic regularization were lower than our prescription, some divergences would remain. If the order were higher, say, under the conventional 4th-order regularization, more terms than necessary would be subtracted off, leading to an unphysical negative energy density and the trace anomaly simultaneously. Full article
Show Figures

Figure 1

12 pages, 252 KiB  
Article
The Geometric Proca–Weyl Field as a Candidate for Dark Matter
by Mauro Duarte, Fábio Dahia and Carlos Romero
Universe 2025, 11(2), 34; https://doi.org/10.3390/universe11020034 - 22 Jan 2025
Viewed by 558
Abstract
We consider the Weyl invariant theory of gravity as an alternative approach to the problem of the origin of dark matter. According to this theory, the geometric Weyl 1-form effectively behaves as a Proca field. In this work, our starting point is to [...] Read more.
We consider the Weyl invariant theory of gravity as an alternative approach to the problem of the origin of dark matter. According to this theory, the geometric Weyl 1-form effectively behaves as a Proca field. In this work, our starting point is to consider the existence of a gas of Weyl–Proca particles in a Bose–Einstein condensate and investigate its behavior in a cosmological context. The results obtained show that, for appropriate values of the free parameter of the model, the Weyl field behaves approximately as a dust fluid in the matter-dominated era as expected for a dark matter candidate. Full article
15 pages, 353 KiB  
Article
Constraints on Metastable Dark Energy Decaying into Dark Matter
by Jônathas S. T. de Souza, Gustavo S. Vicente and Leila L. Graef
Universe 2024, 10(9), 371; https://doi.org/10.3390/universe10090371 - 18 Sep 2024
Cited by 1 | Viewed by 1050
Abstract
We revisit the proposal that an energy transfer from dark energy into dark matter can be described in field theory by a first order phase transition. We analyze a metastable dark energy model proposed in the literature, using updated constraints on the decay [...] Read more.
We revisit the proposal that an energy transfer from dark energy into dark matter can be described in field theory by a first order phase transition. We analyze a metastable dark energy model proposed in the literature, using updated constraints on the decay time of a metastable dark energy from recent data. The results of our analysis show no prospects for potentially observable signals that could distinguish this scenario from the ΛCDM. We analyze, for the first time, the process of bubble nucleation in this model, showing that such model would not drive a complete transition to a dark matter dominated phase even in a distant future. Nevertheless, the model is not excluded by the latest data and we confirm that the mass of the dark matter particle that would result from such a process corresponds to the mass of an axion-like particle, which is currently one of the best motivated dark matter candidates. We argue that extensions to this model, possibly with additional couplings, still deserve further attention as it could provide an interesting and viable description for an interacting dark sector scenario based in a single scalar field. Full article
Show Figures

Figure 1

6 pages, 226 KiB  
Communication
The de Sitter Swampland Conjectures in the Context of Chaplygin-Inspired Inflation
by Orfeu Bertolami, Robertus Potting and Paulo M. Sá
Universe 2024, 10(7), 271; https://doi.org/10.3390/universe10070271 - 23 Jun 2024
Cited by 2 | Viewed by 771
Abstract
In this work, we discuss the de Sitter swampland conjectures in the context of the generalized Chaplygin-inspired inflationary model. We demonstrate that these conjectures can be satisfied, but only in the region of the parameter space far away from the General Relativity limit. [...] Read more.
In this work, we discuss the de Sitter swampland conjectures in the context of the generalized Chaplygin-inspired inflationary model. We demonstrate that these conjectures can be satisfied, but only in the region of the parameter space far away from the General Relativity limit. The cosmic microwave background data had already been found to restrict the allowed inflationary potentials of this model. Our results impose a further limitation on the possible potentials. Full article
10 pages, 263 KiB  
Article
Cosmic Strings from Thermal Inflation
by Robert Brandenberger and Aline Favero
Universe 2024, 10(6), 253; https://doi.org/10.3390/universe10060253 - 4 Jun 2024
Viewed by 890
Abstract
Thermal inflation was proposed as a mechanism to dilute the density of cosmological moduli. Thermal inflation is driven by a complex scalar field possessing a large vacuum expectation value and a very flat potential, called a “flaton”. Such a model admits cosmic string [...] Read more.
Thermal inflation was proposed as a mechanism to dilute the density of cosmological moduli. Thermal inflation is driven by a complex scalar field possessing a large vacuum expectation value and a very flat potential, called a “flaton”. Such a model admits cosmic string solutions, and a network of such strings will inevitably form in the symmetry breaking phase transition at the end of the period of thermal inflation. We discuss the differences of these strings compared to the strings which form in the Abelian Higgs model. Specifically, we find that the upper bound on the symmetry breaking scale is parametrically lower than in the case of Abelian Higgs strings, and that the lower cutoff on the string loop distribution is determined by cusp annihilation rather than by gravitational radiation (for the value of the transition temperature proposed in the original work on thermal inflation). Full article
21 pages, 370 KiB  
Article
The Equation of State of Novel Double-Field Pure K-Essence for Inflation, Dark Matter and Dark Energy
by Changjun Gao
Universe 2024, 10(6), 235; https://doi.org/10.3390/universe10060235 - 24 May 2024
Cited by 2 | Viewed by 883
Abstract
K-essence theories are usually studied in the framework of a single scalar field ϕ. Namely, the Lagrangian of K-essence is the function of the single scalar field ϕ and its covariant derivative. However, in this paper, we explore a double-field pure K-essence, [...] Read more.
K-essence theories are usually studied in the framework of a single scalar field ϕ. Namely, the Lagrangian of K-essence is the function of the single scalar field ϕ and its covariant derivative. However, in this paper, we explore a double-field pure K-essence, i.e., the corresponding Lagrangian is the function of covariant derivatives of double scalar fields without a dependency on scalar fields themselves. This is why we call it double-field pure K-essence. The novelty of this K-essence is that its Lagrangian contains the quotient term of the kinetic energies from the two scalar fields. This results in the presence of many interesting features; for example, the equation of state can be arbitrarily small and arbitrarily large. In comparison, the range of the equation of state for quintessence is 1 to +1. Interestingly, this novel K-essence can play the role of an inflation field, dark matter, or dark energy by appropriately selecting the expressions of Lagrangian. Full article
Show Figures

Figure 1

Back to TopTop