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Probing the Dark Universe with Theory and Observations

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

Deadline for manuscript submissions: closed (30 November 2021) | Viewed by 17786

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Special Issue Editors

Dr. Supriya Pan

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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

Prof. David Fonseca Mota

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Guest Editor

Institute of Theoretical Astrophysics, University of Oslo, 0315 Oslo, Norway
Interests: computational cosmology; numerical simulations; theoretical cosmology; dark energy; cosmology of high energy physics beyond the standard model of particle physics; cosmology of gravity models beyond general relativity

Dr. Weiqiang Yang

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Guest Editor

Department of Physics, Liaoning Normal University, Dalian 116029, China
Interests: computational cosmology; numerical simulations; dark energy; modified gravity theories; neutrino physics

Dr. Jaime Haro Cases

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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

Special Issue Information

Dear Colleagues,

As we all know, the understandings of both early and late expansions of our universe have been the main theme of our present cosmological research. According to a series of recent observational evidences (such as cosmic microwave background radiation, baryon acoustic oscillations, Supernovae Type Ia and some others), almost 96% of the total energy density of the universe is contributed from the dark fluids, namely the dark matter and dark energy, or some geometrical corrections from modified Einstein gravity, but, the nature, origin and the evolutions of these dark fluids are still elusive. The developments in both theoretical foundations and observational data have played an essential role to understand the cosmology better than it was some fifty years back, however, searching for the actual expansion history of the universe is still in progress. In fact, the extreme early phase of the universe (big bang or big bounce or something else?) is also not clear to us.

Thus, in the Special Issue “Probing the Dark Universe with Theory and Observations”, we would like to focus on “what exactly did we know about our universe in the last several decades?” We believe that the discussions in this direction are very relevant for the present time and will be extremely helpful for the next generation of research in the field of cosmology and astrophysics.

It is our great pleasure to serve as the Guest Editors of this Special Issue and we invite our colleagues to submit their works to this Special Issue. In the following we give a series of topics on which we hope our colleagues will be greatly interested in.

Cosmological constraints on (interacting/non-interacting) dark energy and modified gravity models from the latest observational data as well as from the future observational surveys.
Constraining early universe models with observations
Loop quantum cosmology, bouncing cosmologies
N-body simulation.
Variation of the fundamental constants and their effects on the cosmological parameters.

Dr. Supriya Pan
Prof. David F. Mota
Dr. Weiqiang Yang
Prof. Jaume de Haro

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
Interaction
Modified gravity
Bounce
Observations
Future surveys

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Published Papers (7 papers)

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Research

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20 pages, 1077 KiB

Open AccessArticle

Hilltop Inflation and Generation of Helical Magnetic Field

by Sumanta Chakraborty, Supratik Pal and Soumitra SenGupta

Universe 2022, 8(1), 26; https://doi.org/10.3390/universe8010026 - 2 Jan 2022

Cited by 10 | Viewed by 1610

Abstract

Primordial magnetic field generated in the inflationary era can act as a viable source for the present day intergalactic magnetic field of sufficient strength. We present a fundamental origin for such a primordial generation of the magnetic field, namely through anomaly cancellation of [...] Read more.

U (1)

gauge field in quantum electrodynamics in the context of hilltop inflation. We have analysed at length the power spectrum of the magnetic field, thus generated, which turns out to be helical in nature. We have also found that magnetic power spectrum has significant scale-dependence giving rise to a non-trivial magnetic spectral index, a key feature of this model. Interestingly, there exists a large parameter space, where magnetic field of significant strength can be produced. Full article

(This article belongs to the Special Issue Probing the Dark Universe with Theory and Observations)

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Figure 1

12 pages, 608 KiB

Open AccessArticle

Dynamics in Interacting Scalar-Torsion Cosmology

by Andronikos Paliathanasis

Universe 2021, 7(7), 244; https://doi.org/10.3390/universe7070244 - 14 Jul 2021

Cited by 14 | Viewed by 1949

Abstract

In a spatially flat Friedmann–Lemaître–Robertson–Walker background space, we consider a scalar-torsion gravitational model which has similar properties to the dilaton theory. This teleparallel model is invariant under a discrete transformation similar to the Gasperini–Veneziano duality transformation. Moreover, in the gravitational action integral, we introduce the Lagrangian function of a pressureless fluid source which is coupled to the teleparallel dilaton field. This specific gravitational theory with interaction in the dark sector of the universe was investigated by using methods of the dynamical system analysis. We calculate that the theory provides various areas of special interest for the evolution of the cosmological history. Inflationary scaling solutions and the de Sitter universe are recovered. Furthermore, we calculate that there exist an attractor which provides a stable solution where the two fluid components, the scalar field and the pressureless matter, contribute in the cosmological fluid. This solution is of special interest because it can describe the present epoch. Finally, the qualitative evolution of the cosmographic parameters is discussed. Full article

(This article belongs to the Special Issue Probing the Dark Universe with Theory and Observations)

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16 pages, 1176 KiB

Open AccessArticle

Dynamical Stability and Geometrical Diagnostic of the Power Law K-Essence Dark Energy Model with Interaction

by Bo-Hai Chen, Ya-Bo Wu, Dong-Fang Xu, Wei Dong and Nan Zhang

Universe 2020, 6(12), 244; https://doi.org/10.3390/universe6120244 - 18 Dec 2020

Cited by 4 | Viewed by 1961

Abstract

We investigate the cosmological evolution of the power law k-essence dark energy (DE) model with interaction in FRWL spacetime with the Lagrangian that contains a kinetic function

F (X) = - \sqrt{X} + X

. Concretely, the cosmological evolution in this [...] Read more.

We investigate the cosmological evolution of the power law k-essence dark energy (DE) model with interaction in FRWL spacetime with the Lagrangian that contains a kinetic function

F (X) = - \sqrt{X} + X

. Concretely, the cosmological evolution in this model are discussed by the autonomous dynamical system and its critical points, together with the corresponding cosmological quantities, such as

Ω_{ϕ}

w_{ϕ}

c_{s}^{2}

, and q, are calculated at each critical point. The evolutionary trajectories are drawn in order to show the dynamical process on the phases plan around the critical points. The result that we obtained indicates that there are four dynamical attractors, and all of them correspond to an accelerating expansion of universe for certain potential parameter and coupling parameter. Besides that, the geometrical diagnostic by the statefinder hierarchy

S_{3}^{(1)}

and

S_{4}^{(1)}

of this scalar field model are numerically obtained by the phase components, as an extended null diagnostic for the cosmological constant. This diagnostic shows that both the potential parameter

λ

and interaction parameter

α

play important roles in the evolution of the statefinder hierarchy. Full article

(This article belongs to the Special Issue Probing the Dark Universe with Theory and Observations)

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Figure 1

15 pages, 1222 KiB

Open AccessArticle

Model Independent Diagnostics in Interacting Dark Energy Models

by Ying Jiang, Zhongxu Han, Qian Zhang, Weiqiang Yang, Yabo Wu, Jinyang Li, Han Lou, Chenchen Zhao and Yan Wang

Universe 2020, 6(4), 49; https://doi.org/10.3390/universe6040049 - 30 Mar 2020

Cited by 6 | Viewed by 2246

Abstract

In this paper, we have explored non-gravitational interaction dark energy model between dark energy and cold dark matter (CDM). The main purpose of this work is to explore the deviations from

Λ C D M

and to distinguish the evolution trajectory of the [...] Read more.

In this paper, we have explored non-gravitational interaction dark energy model between dark energy and cold dark matter (CDM). The main purpose of this work is to explore the deviations from

Λ C D M

and to distinguish the evolution trajectory of the interaction dark energy model with different parameters. Six forms of interaction were focused on. We have analyzed the deceleration parameters of the coupled model and explored the theoretical models through

s t a t e f i n d e r h i e r a r c h y

and the

O m

diagnostic. We have considered that the Equation of State (EoS) parameter w and parameter

ξ

take different values on the interaction dark energy model respectively and keep another parameter unchanged. It was found that

q_{(z)}

is the worst of the four diagnoses.

O m

S_{3}^{(1)}

and

S_{4}^{(1)}

are good tools to distinguish the interaction dark energy model from

Λ C D M

S_{3}^{(1)}

is a better diagnostic tool when the state parameter w changes and the coupling parameter

ξ

is fixed, while

S_{4}^{(1)}

works better when the coupling parameter

ξ

changes and the state parameter w is fixed. Full article

(This article belongs to the Special Issue Probing the Dark Universe with Theory and Observations)

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23 pages, 3906 KiB

Open AccessArticle

Observational Constraints on Dynamical Dark Energy with Pivoting Redshift

by Weiqiang Yang, Supriya Pan, Eleonora Di Valentino and Emmanuel N. Saridakis

Universe 2019, 5(11), 219; https://doi.org/10.3390/universe5110219 - 16 Nov 2019

Cited by 30 | Viewed by 3097

Abstract

We investigate the generalized Chevallier–Polarski–Linder (CPL) parametrization, which contains the pivoting redshift

z_{p}

as an extra free parameter, in order to examine whether the evolution of the dark energy equation of state can be better described by a different parametrization. We use [...] Read more.

We investigate the generalized Chevallier–Polarski–Linder (CPL) parametrization, which contains the pivoting redshift

z_{p}

as an extra free parameter, in order to examine whether the evolution of the dark energy equation of state can be better described by a different parametrization. We use various data combinations from cosmic microwave background (CMB), baryon acoustic oscillations (BAO), redshift space distortion (RSD), weak lensing (WL), joint light curve analysis (JLA), and cosmic chronometers (CC), and we include a Gaussian prior on the Hubble constant value, in order to extract the observational constraints on various quantities. For the case of free

z_{p}

we find that for all data combinations it always remains unconstrained, and there is a degeneracy with the value of the dark energy equation of state

w_{0}^{p}

z_{p}

. For the case where

z_{p}

is fixed to specific values, and for the full data combination, we find that with increasing

z_{p}

the mean value of

w_{0}^{p}

slowly moves into the phantom regime, however the cosmological constant is always allowed within 1

σ

confidence-level. In fact, the significant effect is that with increasing

z_{p}

, the correlations between

w_{0}^{p}

and

w_{a}

(the free parameter of the dark energy equation of state quantifying its evolution with redshift), change from negative to positive, with the case

z_{p} = 0.35

corresponding to no correlation. The fact that the two parameters describing the dark energy equation of state are uncorrelated for

z_{p} = 0.35

justifies why a non-zero pivoting redshift needs to be taken into account. Full article

(This article belongs to the Special Issue Probing the Dark Universe with Theory and Observations)

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16 pages, 447 KiB

Open AccessArticle

Graviton Spectrum in Simplified Dark Matter Models with Graviton Mediators in the de Sitter Space

by Ion Vasile Vancea

Universe 2019, 5(1), 39; https://doi.org/10.3390/universe5010039 - 20 Jan 2019

Cited by 1 | Viewed by 2611

Abstract

This is the second in a series of papers investigating the formulation of the simplified Dark Matter models with graviton mediators in cosmological backgrounds. We address here the crucial problem of the fundamental observable of interest, namely the graviton spectrum in an Friedmann–Lemaître–Robertson–Walker (FLRW) cosmological background with an arbitrary Dark Matter background component. We calculate the correction to the free graviton two-point function up to the second order in the coupling constant between the Dark Matter and the graviton in the simplified Dark Matter model with graviton mediators approach in the de Sitter space. Our result is model independent in the sense that it does not depend on the particular form of the Dark Matter fields. In addition, due to the universality of the interaction between the Dark Matter and the graviton, the result obtained here applies to the interaction between the baryonic matter and the gravitons. As an application, we discuss in detail the massive scalar Dark Matter model and calculate the first order correction to the two-point function due to two Dark Matter modes in the adiabatic regime. Full article

(This article belongs to the Special Issue Probing the Dark Universe with Theory and Observations)

Review

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41 pages, 6929 KiB

Open AccessReview

Taxonomy of Dark Energy Models

by Verónica Motta, Miguel A. García-Aspeitia, Alberto Hernández-Almada, Juan Magaña and Tomás Verdugo

Universe 2021, 7(6), 163; https://doi.org/10.3390/universe7060163 - 26 May 2021

Cited by 45 | Viewed by 2907

Abstract

The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational experiments with increasing precision in its measurements. However, the most accepted model for explaining the dynamic of our Universe, the so-called Lambda cold dark matter, faces several problems related to the nature of such energy component. This has led to a growing exploration of alternative models attempting to solve those drawbacks. In this review, we briefly summarize the characteristics of a (non-exhaustive) list of dark energy models as well as some of the most used cosmological samples. Next, we discuss how to constrain each model’s parameters using observational data. Finally, we summarize the status of dark energy modeling. Full article

(This article belongs to the Special Issue Probing the Dark Universe with Theory and Observations)

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