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Universe
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Universe: Feature Papers 2024—'Cosmology'
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Universe: Feature Papers 2024—'Cosmology'

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

Deadline for manuscript submissions: 31 December 2024 | Viewed by 5798

Special Issue Editors

Dr. Jaime Haro Cases

E-Mail Website
Guest Editor
Department of mathematics , Politechnic University of Catalonia, Barcelona, Spain
Interests: quintessential inflation and gravitational particle production
Special Issues, Collections and Topics in MDPI journals
Dr. Supriya Pan

E-Mail Website
Guest Editor
Department of Mathematics, Presidency University, 86/1 College Street, Kolkata 700073, India
Interests: theoretical and observational cosmology; dark energy; modified gravity theories; matter creation; massive neutrinos
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We are pleased to announce that Cosmology is now compiling a collection of papers submitted by the Editorial Board Members (EBMs) of our section and outstanding scholars in this research field. We welcome contributions and recommendations from EBMs.

This Special Issue aims to set itself at the cutting edge of the most recent advances in the intertwined ties of cosmology with other fields at all relevant scales from mutually fertilizing theoretical, phenomenological, and experimental perspectives. We expect these papers to be widely read and highly influential within the field. Potential topics include, but are not limited to, the following: cosmological models, quantum cosmology, dark matter, dark energy, cosmological perturbation theory, cosmic microwave background (CMB), observational cosmology, cosmological tensions, etc.

We would also like to take this opportunity to ask more scholars to join the section Cosmology, so that we can work together to further develop this exciting field of research.

Dr. Jaime Haro Cases
Dr. Supriya Pan
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 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

  • cosmological models
  • quantum cosmology
  • dark matter and dark energy
  • cosmic acceleration
  • cosmological constants
  • cosmological perturbation theory
  • cosmic microwave background (CMB)
  • observational cosmology

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Published Papers (6 papers)

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Research

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28 pages, 21146 KiB  
Article
Combined Studies Approach to Rule Out Cosmological Models Which Are Based on Nonlinear Electrodynamics
by Ricardo García-Salcedo, Isidro Gómez-Vargas, Tame González, Vicent Martinez-Badenes and Israel Quiros
Universe 2024, 10(9), 353; https://doi.org/10.3390/universe10090353 - 4 Sep 2024
Viewed by 646
Abstract
We apply a combined study in order to investigate the dynamics of cosmological models incorporating nonlinear electrodynamics (NLED). The study is based on the simultaneous investigation of such fundamental aspects as stability and causality, complemented with a dynamical systems investigation of the involved [...] Read more.
We apply a combined study in order to investigate the dynamics of cosmological models incorporating nonlinear electrodynamics (NLED). The study is based on the simultaneous investigation of such fundamental aspects as stability and causality, complemented with a dynamical systems investigation of the involved models, as well as Bayesian inference for parameter estimation. We explore two specific NLED models: the power-law and the rational Lagrangian. We present the theoretical framework of NLED coupled with general relativity, followed by an analysis of the stability and causality of the various NLED Lagrangians. We then perform a detailed dynamical analysis to identify the ranges where these models are stable and causal. Our results show that the power-law Lagrangian model transitions through various cosmological phases, evolving from a Maxwell radiation-dominated state to a matter-dominated state. For the rational Lagrangian model, including the Maxwell term, stable and causal behavior is observed within specific parameter ranges, with critical points indicating the evolutionary pathways of the universe. To validate our theoretical findings, we perform Bayesian parameter estimation using a comprehensive set of observational data, including cosmic chronometers, baryon acoustic oscillation (BAO) measurements, and supernovae type Ia (SNeIa). The estimated parameters for both models align with the expected values for the current universe, particularly the matter density Ωm and the Hubble parameter h. However, the parameters of the models are not tightly constrained within the prior ranges. Our combined studies approach rules out the mentioned models as an appropriate description of the cosmos. Our results highlight the need for further refinement and exploration of NLED-based cosmological models to fully integrate them into the standard cosmological framework. Full article
(This article belongs to the Special Issue Universe: Feature Papers 2024—'Cosmology')
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34 pages, 17795 KiB  
Article
Lorentzian Quantum Cosmology from Effective Spin Foams
by Bianca Dittrich and José Padua-Argüelles
Universe 2024, 10(7), 296; https://doi.org/10.3390/universe10070296 - 13 Jul 2024
Cited by 13 | Viewed by 927
Abstract
Effective spin foams provide the most computationally efficient spin foam models yet and are therefore ideally suited for applications, e.g., to quantum cosmology. Here, we provide the first effective spin foam computations of a finite time evolution step in a Lorentzian quantum de [...] Read more.
Effective spin foams provide the most computationally efficient spin foam models yet and are therefore ideally suited for applications, e.g., to quantum cosmology. Here, we provide the first effective spin foam computations of a finite time evolution step in a Lorentzian quantum de Sitter universe. We will consider a setup that computes the no-boundary wave function and a setup describing the transition between two finite scale factors. A key property of spin foams is that they implement discrete spectra for the areas. We therefore study the effects that are induced by the discrete spectra. To perform these computations, we had to identify a technique to deal with highly oscillating and slowly converging or even diverging sums. Here, we illustrate that high-order Shanks transformation works very well and is a promising tool for the evaluation of Lorentzian (gravitational) path integrals and spin foam sums. Full article
(This article belongs to the Special Issue Universe: Feature Papers 2024—'Cosmology')
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22 pages, 785 KiB  
Article
Constraints on the Minimally Extended Varying Speed of Light Model Using Pantheon+ Dataset
by Seokcheon Lee
Universe 2024, 10(6), 268; https://doi.org/10.3390/universe10060268 - 19 Jun 2024
Cited by 6 | Viewed by 1185
Abstract
In the context of the minimally extended varying speed of light (meVSL) model, both the absolute magnitude and the luminosity distance of type Ia supernovae (SNe Ia) deviate from those predicted by general relativity (GR). Using data from the Pantheon+ survey, we assess [...] Read more.
In the context of the minimally extended varying speed of light (meVSL) model, both the absolute magnitude and the luminosity distance of type Ia supernovae (SNe Ia) deviate from those predicted by general relativity (GR). Using data from the Pantheon+ survey, we assess the plausibility of various dark energy models within the framework of meVSL. Both the constant equation of state (EoS) of the dark energy model (ωCDM) and the Chevallier–Polarski–Linder (CPL) parameterization model (ω=ω0+ωa(1−a)) indicate potential variations in the cosmic speed of light at the 1−σ confidence level. For Ωm0=0.30,0.31, and 0.32 with (ω0,ωa)=(−1,0), the 1−σ range of c˙0/c0(10−13yr−1) is (−8.76, −0.89), (−11.8, 3.93), and (−14.8, −6.98), respectively. Meanwhile, the 1−σ range of c˙0/c0(10−12yr−1) for CPL dark energy models with −1.05≤ω0≤−0.95 and 0.28≤Ωm0≤0.32 is (−6.31, −2.98). The value of c at z=3 can exceed that of the present by 0.2∼3% for ωCDM models and 5∼13% for CPL models. Additionally, for viable models except for the CPL model with Ωm0=0.28, we find −25.6≤G˙0/G0(10−12yr−1)≤−0.36. For this particular model, we obtain an increasing rate of the gravitational constant within the range 1.65≤G˙0/G0(10−12yr−1)≤3.79. We obtain some models that do not require dark matter energy density through statistical interpretation. However, this is merely an effect of the degeneracy between model parameters and energy density and does not imply that dark matter is unnecessary. Full article
(This article belongs to the Special Issue Universe: Feature Papers 2024—'Cosmology')
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15 pages, 1433 KiB  
Article
Fast Radio Burst Energy Function in the Presence of DMhost Variation
by Ji-Guo Zhang, Yichao Li, Jia-Ming Zou, Ze-Wei Zhao, Jing-Fei Zhang and Xin Zhang
Universe 2024, 10(5), 207; https://doi.org/10.3390/universe10050207 - 6 May 2024
Cited by 4 | Viewed by 978
Abstract
Fast radio bursts (FRBs) have been found in great numbers, but the physical mechanism of these sources is still a mystery. The redshift evolutions of the FRB energy distribution function and the volumetric rate shed light on the origin of FRBs. However, such [...] Read more.
Fast radio bursts (FRBs) have been found in great numbers, but the physical mechanism of these sources is still a mystery. The redshift evolutions of the FRB energy distribution function and the volumetric rate shed light on the origin of FRBs. However, such estimations rely on the dispersion measurement (DM)–redshift (z) relationship. A few FRBs that have been detected recently show large excess DMs beyond the expectation from the cosmological and Milky Way contributions, which indicates large spread of DMs from their host galaxies. In this work, we adopt two lognormal-distributed DMhost models and estimate the energy function using the non-repeating FRBs selected from the Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB Catalog 1. By comparing the lognormal-distributed DMhost models to a constant DMhost model, the FRB energy function results are consistent within the measurement uncertainty. We also estimate the volumetric rate of the non-repeating FRBs in three different redshift bins. The volumetric rate shows that the trend is consistent with the stellar-mass density redshift evolution. Since the lognormal-distributed DMhost model increases the measurement errors, the inference of FRBs tracking the stellar-mass density is nonetheless undermined. Full article
(This article belongs to the Special Issue Universe: Feature Papers 2024—'Cosmology')
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Review

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19 pages, 436 KiB  
Review
Different Aspects of Entropic Cosmology
by Shin’ichi Nojiri, Sergei D. Odintsov and Tanmoy Paul
Universe 2024, 10(9), 352; https://doi.org/10.3390/universe10090352 - 3 Sep 2024
Cited by 2 | Viewed by 594
Abstract
We provide a short review of the recent developments in entropic cosmology based on two thermodynamic laws of the apparent horizon, namely the first and the second laws of thermodynamics. The first law essentially provides the change in entropy of the apparent horizon [...] Read more.
We provide a short review of the recent developments in entropic cosmology based on two thermodynamic laws of the apparent horizon, namely the first and the second laws of thermodynamics. The first law essentially provides the change in entropy of the apparent horizon during the cosmic evolution of the universe; in particular, it is expressed by TdS=−d(ρV)+WdV (where W is the work density and other quantities have their usual meanings). In this way, the first law actually links various theories of gravity with the entropy of the apparent horizon. This leads to a natural question—“What is the form of the horizon entropy corresponding to a general modified theory of gravity?”. The second law of horizon thermodynamics states that the change in total entropy (the sum of horizon entropy + matter fields’ entropy) with respect to cosmic time must be positive, where the matter fields behave like an open system characterised by a non-zero chemical potential. The second law of horizon thermodynamics importantly provides model-independent constraints on entropic parameters. Finally, we discuss the standpoint of entropic cosmology on inflation (or bounce), reheating and primordial gravitational waves from the perspective of a generalised entropy function. Full article
(This article belongs to the Special Issue Universe: Feature Papers 2024—'Cosmology')
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26 pages, 388 KiB  
Review
Introduction to the Number of e-Folds in Slow-Roll Inflation
by Alessandro Di Marco, Emanuele Orazi and Gianfranco Pradisi
Universe 2024, 10(7), 284; https://doi.org/10.3390/universe10070284 - 29 Jun 2024
Cited by 1 | Viewed by 841
Abstract
In this review, a pedagogical introduction to the concepts of slow-roll inflationary universe and number of e-folds is provided. In particular, the differences between the basic notion of number of e-folds (Ne), total number of e-folds ( [...] Read more.
In this review, a pedagogical introduction to the concepts of slow-roll inflationary universe and number of e-folds is provided. In particular, the differences between the basic notion of number of e-folds (Ne), total number of e-folds (NT) and number of e-folds before the end of inflation (N) are outlined. The proper application of the number of e-folds before the end of inflation is discussed both as a time-like variable for the scalar field evolution and as a key parameter for computing inflationary predictions. Full article
(This article belongs to the Special Issue Universe: Feature Papers 2024—'Cosmology')
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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: Radio observations as a probe of cosmic web magnetism
Authors: Ettore Carretti; Franco Vazza
Affiliation: INAF - Istituto di Radioastronomia, Bologna, Italy Università di Bologna, Bologna, Italy
Abstract: -

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