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Symmetry
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Revealing the Symmetries of the Universe: Dark Energy, Inflation and...
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Revealing the Symmetries of the Universe: Dark Energy, Inflation and Modified Gravity

A special issue of Symmetry (ISSN 2073-8994).

Deadline for manuscript submissions: closed (31 July 2016) | Viewed by 20474

Special Issue Editors

Prof. Dr. Shin'ichi Nojiri

grade E-Mail Website
Guest Editor
1. Department of Physics, Nagoya University, Nagoya 464-8602, Japan
2. Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602, Japan
Interests: particle cosmology; quantum field theory; theoretical physics; quantum gravity; modified gravity
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,

Our perception for the Universe has drastically changed the last twenty years, since observations revealed that the Universe is expanding in an accelerating way. Ever since then, the challenge in modern theoretical cosmology is to describe the two accelerations eras that our Universe has experienced in its evolution; that is, the inflationary era and the late-time acceleration eras, with the latter being attributed to a negative pressure fluid. Modified gravity provides a consistent description of these two acceleration eras, and sometimes with the same theoretical framework; however, the challenge is to achieve concordance with the latest observational data. In addition, many theoretical problems in cosmology remain unsolved, such as baryogenesis and also dark matter issues. The aim of this Special Issue is twofold: Firstly to provide an informative update of the successful modified gravity description of the cosmos, and secondly to present how modified gravity addresses the current theoretical challenges in cosmology. To this end, many theoretical physics and astroparticle physics techniques have to be employed in order to reveal the most optimal description of the Universe.

We are very pleased to receive submissions to this Special Issue on modified gravity theories, dark energy models, astroparticle cosmological descriptions, and, related to these disciplines, physical descriptions.

Prof. Dr. Shin’ichi Nojiri
Dr. Vasilis K. Oikonomou
Guest Editor

Manuscript Submission Information

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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.

Keywords

  • Modified theories of gravity
  • Higher-dimensional gravity and other theories of gravity
  • Loop quantum gravity and quantum gravity
  • Bouncing cosmologies
  • Dark energy
  • Cosmology
  • Gravitational baryogenesis
  • Bouncing cosmology and ekpyrotic scenarios
  • Loop quantum cosmology
  • Particle-theory and field-theory models of the early Universe
  • Neutrinos cosmological implications
  • Inflationary universe, gauge field theories and models beyond the standard model
  • Quantum fields in curved space-time

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Published Papers (4 papers)

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Research

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22 pages, 326 KiB  
Article
On the Magnetic Evolution in Friedmann Universes and the Question of Cosmic Magnetogenesis
by Christos G. Tsagas
Symmetry 2016, 8(11), 122; https://doi.org/10.3390/sym8110122 - 9 Nov 2016
Cited by 21 | Viewed by 3563
Abstract
We analyse the evolution of primordial magnetic fields in spatially flat Friedmann universes and reconsider the belief that, after inflation, these fields decay adiabatically on all scales. Without abandoning classical electromagnetism or standard cosmology, we demonstrate that this is not necessarily the case [...] Read more.
We analyse the evolution of primordial magnetic fields in spatially flat Friedmann universes and reconsider the belief that, after inflation, these fields decay adiabatically on all scales. Without abandoning classical electromagnetism or standard cosmology, we demonstrate that this is not necessarily the case for superhorizon-sized magnetic fields. The underlying reason for this is causality, which confines the post-inflationary process of electric-current formation, electric-field elimination and magnetic-flux freezing within the horizon. As a result, the adiabatic magnetic decay is not a priori guaranteed on super-Hubble scales. Instead, after inflation, large-scale magnetic fields obey a power-law solution, where one of the modes drops at a rate slower than the adiabatic. Whether this slowly decaying mode can dominate and dictate the post-inflationary magnetic evolution depends on the initial conditions. These are determined by the evolution of the field during inflation and by the nature of the transition from the de Sitter phase to the reheating era and then to the subsequent epochs of radiation and dust. We discuss two alternative and complementary scenarios to illustrate the role and the implications of the initial conditions for cosmic magnetogenesis. Our main claim is that magnetic fields can be superadiabatically amplified after inflation, as long as they remain outside the horizon. This means that inflation-produced fields can reach astrophysically relevant residual strengths without breaking away from standard physics. Moreover, using the same causality arguments, one can constrain (or in some cases assist) the non-conventional scenarios of primordial magnetogenesis that amplify their fields during inflation. Finally, we show that our results extend naturally to the marginally open and the marginally closed Friedmann universes. Full article
(This article belongs to the Special Issue Revealing the Symmetries of the Universe: Dark Energy, Inflation and Modified Gravity)
17 pages, 3112 KiB  
Article
Higgs Phase in a Gauge U(1) Non-Linear CP1-Model. Two Species of BPS Vortices and Their Zero Modes
by Alberto Alonso-Izquierdo and Juan Mateos-Guilarte
Symmetry 2016, 8(9), 91; https://doi.org/10.3390/sym8090091 - 1 Sep 2016
Cited by 3 | Viewed by 4844
Abstract
In this paper, zero modes of fluctuation are dissected around the two species of BPS vortices existing in the critical Higgs phase, where the scalar and vector meson masses are equal, of a gauged U ( 1 ) nonlinear CP 1 -model. If [...] Read more.
In this paper, zero modes of fluctuation are dissected around the two species of BPS vortices existing in the critical Higgs phase, where the scalar and vector meson masses are equal, of a gauged U ( 1 ) nonlinear CP 1 -model. If 2 π n , n ∈ Z , is the quantized magnetic flux of the two species of BPS vortex solutions, 2 n linearly-independent vortex zero modes for each species are found and described. The existence of two species of moduli spaces of dimension 2 n of these stringy topological defects is thus locally shown. Full article
(This article belongs to the Special Issue Revealing the Symmetries of the Universe: Dark Energy, Inflation and Modified Gravity)
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9 pages, 155 KiB  
Article
Is the Hawking Quasilocal Energy “Newtonian”?
by Valerio Faraoni
Symmetry 2015, 7(4), 2038-2046; https://doi.org/10.3390/sym7042038 - 5 Nov 2015
Cited by 13 | Viewed by 4088
Abstract
The Misner–Sharp–Hernandez mass defined in general relativity and in spherical symmetry has been recognized as having a Newtonian character in previous literature. In order to better understand this feature we relax spherical symmetry and we study the generalization of the Misner–Sharp–Hernandez mass to [...] Read more.
The Misner–Sharp–Hernandez mass defined in general relativity and in spherical symmetry has been recognized as having a Newtonian character in previous literature. In order to better understand this feature we relax spherical symmetry and we study the generalization of the Misner–Sharp–Hernandez mass to general spacetimes, i.e., the Hawking quasilocal mass. The latter is decomposed into a matter contribution and a contribution coming solely from the Weyl tensor. The Weyl tensor is then decomposed into an electric part (which has a Newtonian counterpart) and a magnetic one (which does not), which further splits the quasilocal mass into “Newtonian” and “non-Newtonian” parts. Only the electric (Newtonian) part contributes to the quasilocal mass. Full article
(This article belongs to the Special Issue Revealing the Symmetries of the Universe: Dark Energy, Inflation and Modified Gravity)

Review

Jump to: Research

22 pages, 868 KiB  
Review
Big Bounce Genesis and Possible Experimental Tests: A Brief Review
by Yeuk-Kwan Edna Cheung, Changhong Li and Joannis D. Vergados
Symmetry 2016, 8(11), 136; https://doi.org/10.3390/sym8110136 - 23 Nov 2016
Cited by 20 | Viewed by 6576
Abstract
We review the recent status of big bounce genesis as a new possibility of using dark matter particles’ mass and interaction cross-section to test the existence of a bounce universe at the early stage of evolution in our currently-observed universe. To study the [...] Read more.
We review the recent status of big bounce genesis as a new possibility of using dark matter particles’ mass and interaction cross-section to test the existence of a bounce universe at the early stage of evolution in our currently-observed universe. To study the dark matter production and evolution inside the bounce universe, called big bounce genesis for short, we propose a model independent approach. We shall present the motivation for proposing big bounce, as well as the model independent predictions, which can be tested by dark matter direct searches. A positive finding shall have profound impact on our understanding of the early universe physics. Full article
(This article belongs to the Special Issue Revealing the Symmetries of the Universe: Dark Energy, Inflation and Modified Gravity)
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