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Symmetry
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Inflation, Universe symmetries and Modified gravity
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Inflation, Universe symmetries and Modified gravity

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Physics".

Deadline for manuscript submissions: closed (1 November 2019) | Viewed by 10878

Special Issue Editor

Prof. Dr. Vasilis K. Oikonomou

E-Mail Website
Guest Editor
Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
Interests: cosmology; inflationary cosmology; modified theories of gravity; physics of the early universe; dark energy; dark matter; supersymmetry; mathematical physics; high energy physics; theoretical physics; epistemic game theory; game theory
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The early-time acceleration era is one of the most mysterious and interesting eras of our Universe's evolution, since it can still be described by classical physics without invoking any quantum gravity arguments, or at least these can be introduced as perturbative effects. The fact that classical physics can still describe this early acceleration era, enables us to constrain this era by using several observable quantities. This era is dubbed as inflationary era, and the whole inflation concept solved initially the shortcomings of the standard Big Bang cosmology. After the latest Planck data, the viable models of inflation have been seriously reduced in number. The original inflationary scenario was referring to a slow-rolling canonical scalar field, but this is not the only possibility, since generalizations of various modified gravity theories and alternative scalar-tensor theories may also describe and produce a viable inflationary era. With this special issue we aim to provide a rigid and consistent overview of the various inflationary scenarios, combining several theoretical frameworks, thus creating a timely, pedagogical, introductive but also effective database to inflationary theories techniques and methods.

Prof. Vasilis K. Oikonomou
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. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). 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.

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Published Papers (3 papers)

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Research

12 pages, 1798 KiB  
Article
Some Interacting Dark Energy Models
by Martiros Khurshudyan and Asatur Zh. Khurshudyan
Symmetry 2018, 10(11), 577; https://doi.org/10.3390/sym10110577 - 2 Nov 2018
Cited by 16 | Viewed by 3389
Abstract
In this paper, we study various cosmological models involving new nonlinear forms of interaction between cold dark matter (DM) and dark energy (DE) assuming that DE is a barotropic fluid. The interactions are nonlinear either due to [...] Read more.
In this paper, we study various cosmological models involving new nonlinear forms of interaction between cold dark matter (DM) and dark energy (DE) assuming that DE is a barotropic fluid. The interactions are nonlinear either due to log ( ρ d e / ρ d m ) or log ( ρ d m / ρ d e ) parameterizations, respectively. The main purpose of this paper is to demonstrate the applicability of the forms of suggested interactions to the problem of modern cosmology known as accelerated expansion of the Universe. Using the differential age of old galaxies expressed in terms of H ( z ) data, the peak position of baryonic acoustic oscillations (known as BAO data), the SN Ia data with strong gravitational lensing data, we obtain the best fit values of the model parameters for each case. Besides, using O m analysis and S 3 parameter from the statefinder hierarchy analysis, we also demonstrate that the considered models are clearly different from the Λ CDM model. We obtain that the models predict Hubble parameter values consistent to the estimations from gravitational lensing, which probes the expansion out to z ≤ 1.7 . We show that, with considered models, we can also explain PLANCK 2015 and PLANCK 2018 experiment results. Full article
(This article belongs to the Special Issue Inflation, Universe symmetries and Modified gravity)
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21 pages, 573 KiB  
Article
Charged and Non-Charged Black Hole Solutions in Mimetic Gravitational Theory
by Gamal G.L. Nashed
Symmetry 2018, 10(11), 559; https://doi.org/10.3390/sym10110559 - 1 Nov 2018
Cited by 15 | Viewed by 3633
Abstract
In this study, we derive, in the framework of mimetic theory, charged and non-charged black hole solutions for spherically symmetric as well as flat horizon spacetimes. The asymptotic behavior of those black holes behave as flat or (A)dS spacetimes and coincide with the [...] Read more.
In this study, we derive, in the framework of mimetic theory, charged and non-charged black hole solutions for spherically symmetric as well as flat horizon spacetimes. The asymptotic behavior of those black holes behave as flat or (A)dS spacetimes and coincide with the solutions derived before in general relativity theory. Using the field equations of non-linear electrodynamics mimetic theory we derive new black hole solutions with monopole and quadrupole terms. The quadruple term of those black holes is related by a constant so that its vanishing makes the solutions coincide with the linear Maxwell black holes. We study the singularities of those solutions and show that they possess stronger singularity than the ones known in general relativity. Among many things, we study the horizons as well as the heat capacity to see if the black holes derived in this study have thermodynamical stability or not. Full article
(This article belongs to the Special Issue Inflation, Universe symmetries and Modified gravity)
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14 pages, 456 KiB  
Article
Impact of Collisional Matter on the Late-Time Dynamics of f(R,T) Gravity
by M. Zubair, Muhammad Zeeshan, Syed Sibet Hasan and V. K. Oikonomou
Symmetry 2018, 10(10), 463; https://doi.org/10.3390/sym10100463 - 5 Oct 2018
Cited by 18 | Viewed by 3096
Abstract
We study the cosmic evolution of non-minimally coupled f ( R , T ) gravity in the presence of matter fluids consisting of collisional self-interacting dark matter and radiation. We study the cosmic evolution in the presence of collisional matter, and we compare [...] Read more.
We study the cosmic evolution of non-minimally coupled f ( R , T ) gravity in the presence of matter fluids consisting of collisional self-interacting dark matter and radiation. We study the cosmic evolution in the presence of collisional matter, and we compare the results with those corresponding to non-collisional matter and the Λ -cold-dark-matter ( Λ CDM) model. Particularly, for a flat Friedmann–Lema i ^ tre–Robertson–Walker Universe, we study two non-minimally coupled f ( R , T ) gravity models and we focus our study on the late-time dynamical evolution of the model. Our study is focused on the late-time behavior of the effective equation of the state parameter ω e f f and of the deceleration parameter q as functions of the redshift for a Universe containing collisional and non-collisional dark matter fluids, and we compare both models with the Λ CDM model. As we demonstrate, the resulting picture is well accommodated to the latest observational data on the basis of physical parameters. Full article
(This article belongs to the Special Issue Inflation, Universe symmetries and Modified gravity)
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