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Universe
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Dark Energy and the Dark Sector in Supergravity, String Theory...
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Dark Energy and the Dark Sector in Supergravity, String Theory and Extra-Dimensions

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

Deadline for manuscript submissions: closed (10 April 2022) | Viewed by 9474

Special Issue Editors

Dr. Ivonne Zavala

E-Mail Website
Guest Editor
Physics Department, Swansea University, Singleton Park, Sketty, Swansea SA2 8PP, UK
Interests: early and late time cosmology; dark energy; inflation; primordial gravitational waves; dark matter; string theory; string cosmology; supergravity; branes
Dr. Giuseppe Dibitetto

E-Mail
Guest Editor
Dipartimento di Fisica e Astronomia, Universita di Padova, Padua, Italy
Interests: string compactifications; dark energy; quintessence models; holography

Special Issue Information

Dear Colleagues,

The latest cosmological data strongly support the phenomenological standard model of cosmology, the ΛCDM model, where Λ stands for a cosmological constant and CDM stands for cold dark matter. According to the ΛCDM model, 68% of the energy density budget in the universe comprises dark energy, which is causing the expansion of the universe to accelerate today, though only 27% of the universe is dark matter while only 5% corresponds to baryonic matter.

In spite of the experimental support, the ΛCDM model lacks an explicit physical theory for the origin or physical nature of the dark sector: dark matter and dark energy.

The aim of this Special Issue is to collect original research contributions regarding the progress in understanding the cosmological dark sector (dark energy and dark matter) in theories beyond the standard models of cosmology and particle physics in a broad sense.

The topics to be discussed include but are not restricted to the following: dark energy and dark matter in supergravity; string theory and other theories BSM, such as extra dimensions and the brane world scenario; coupled models of dark energy and dark matter in these theories; and the dark sector and quantum gravity constraints on cosmological acceleration.

The aim is to describe the state-of-the-art and perspectives in these research fields related to the theme of the Special Issue.

We welcome submissions of research letters and communications as well as reviews on the subjects above.

Dr. Ivonne Zavala
Dr. Giuseppe Dibitetto
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

  • dark energy
  • dark matter
  • coupled dark matter/dark energy models
  • supergravity and string cosmology
  • extra dimensions

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Published Papers (5 papers)

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Research

22 pages, 377 KiB  
Article
Quantum Fluctuations in Vacuum Energy: Cosmic Inflation as a Dynamical Phase Transition
by Masahiro Morikawa
Universe 2022, 8(6), 295; https://doi.org/10.3390/universe8060295 - 24 May 2022
Cited by 2 | Viewed by 2136
Abstract
A variety of models of inflation in the early Universe have been proposed and applied to describe successfully the origin of all possible structures in the Universe. On the other hand, inflation theory is still phenomenological and needs systematic physical foundations, including the [...] Read more.
A variety of models of inflation in the early Universe have been proposed and applied to describe successfully the origin of all possible structures in the Universe. On the other hand, inflation theory is still phenomenological and needs systematic physical foundations, including the relation to dark matter and dark energy. The essence of cosmic inflation would be a dynamical phase transition and the spontaneous symmetry breaking process, which are common in ordinary physics in the laboratory. At the beginning of the phase transition, the system is often in an adiabatic ground state and produces a squeezed state. This is widely interpreted as the generation of classical structures; however, it is not. The common notion of decoherence is not sufficient to describe the inflationary phase transition: a particular trajectory must be singled out in the dynamics. When an interaction turns on, dissipation or the energy flow/cascade is possible, and the c-number random field appears. The separation of these classical statistical fluctuations from the deterministic time evolution is indicated by the secular divergence or the infrared divergence of the system. We describe this phase transition based on the closed-time-path method and derive a quantum Langevin equation with classical noise, which sources the development of a coherent state. Introducing the effective action method to describe the evolution of the coherent state, we describe the order parameter that characterizes the phase transition and the associated spontaneous symmetry breaking. Since this phase transition process is common in physics, we discuss further applications of this formalism in other physical systems. Full article
(This article belongs to the Special Issue Dark Energy and the Dark Sector in Supergravity, String Theory and Extra-Dimensions)
15 pages, 1388 KiB  
Article
Positive Energy and Non-SUSY Flows in ISO(7) Gauged Supergravity
by Giuseppe Dibitetto
Universe 2022, 8(5), 293; https://doi.org/10.3390/universe8050293 - 23 May 2022
Cited by 3 | Viewed by 1588
Abstract
We consider maximal gauged supergravity in 4D with the ISO(7) gauge group, which arises from a consistent truncation of massive IIA supergravity on a six-sphere. Within its G2-invariant sector, the theory is known to possess a supersymmetric AdS [...] Read more.
We consider maximal gauged supergravity in 4D with the ISO(7) gauge group, which arises from a consistent truncation of massive IIA supergravity on a six-sphere. Within its G2-invariant sector, the theory is known to possess a supersymmetric AdS extremum, as well as two non-supersymmetric ones. In this context, we provide a first-order formulation of the theory by making use of the Hamilton–Jacobi (HJ) formalism. This allows us to derive a positive energy theorem for both non-supersymmetric extrema. Subsequently, we also find novel non-supersymmetric domain walls (DWs) interpolating between the supersymmetric extremum and each of the other two. Finally, we discuss a perturbative HJ technique that may be used in order to solve for curved DW geometries. Full article
(This article belongs to the Special Issue Dark Energy and the Dark Sector in Supergravity, String Theory and Extra-Dimensions)
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8 pages, 383 KiB  
Communication
Modified Supergravity Phenomenology in Gravitational Waves Era
by Andrea Addazi and Qingyu Gan
Universe 2022, 8(5), 280; https://doi.org/10.3390/universe8050280 - 12 May 2022
Cited by 1 | Viewed by 1523
Abstract
We discuss phenomenological aspects of modified supergravity (MSG) in gravitational wave (GW) physics. MSG naturally provides double inflation and primordial black holes (PBHs) as cold dark matter. Intriguingly, MSG predicts a large amplification of the scalar and tensor perturbation power spectrum, generating a [...] Read more.
We discuss phenomenological aspects of modified supergravity (MSG) in gravitational wave (GW) physics. MSG naturally provides double inflation and primordial black holes (PBHs) as cold dark matter. Intriguingly, MSG predicts a large amplification of the scalar and tensor perturbation power spectrum, generating a secondary GW stochastic background which can be tested in space-based interferometers. Full article
(This article belongs to the Special Issue Dark Energy and the Dark Sector in Supergravity, String Theory and Extra-Dimensions)
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16 pages, 527 KiB  
Article
Inflationary Implications of the Covariant Entropy Bound and the Swampland de Sitter Conjectures
by Dibya Chakraborty, Cesar Damian, Alberto González Bernal and Oscar Loaiza-Brito
Universe 2021, 7(11), 423; https://doi.org/10.3390/universe7110423 - 6 Nov 2021
Cited by 1 | Viewed by 1373
Abstract
We present a proposal to relate the de Sitter conjecture (dSC) with the time dependence of fluxes via the covariant entropy bound (CEB). By assuming an early phase of accelerated expansion where the CEB is satisfied, we take into account a contribution from [...] Read more.
We present a proposal to relate the de Sitter conjecture (dSC) with the time dependence of fluxes via the covariant entropy bound (CEB). By assuming an early phase of accelerated expansion where the CEB is satisfied, we take into account a contribution from time-dependent flux compactification to the four-dimensional entropy which establishes a bound on the usual slow-roll parameters ηH and ϵH. We also show an explicit calculation of entropy from a toroidal flux compactification, from a transition amplitude of time-dependent fluxes which allows us to determine the conditions on which the bounds on the slow-roll parameters are in agreement to the dSC. Full article
(This article belongs to the Special Issue Dark Energy and the Dark Sector in Supergravity, String Theory and Extra-Dimensions)
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15 pages, 12971 KiB  
Article
Stringy Bubbles Solve de Sitter Troubles
by Per Berglund, Tristan Hübsch and Djordje Minic
Universe 2021, 7(10), 363; https://doi.org/10.3390/universe7100363 - 28 Sep 2021
Cited by 10 | Viewed by 1868
Abstract
Finding four-dimensional de Sitter spacetime solutions in string theory has been a vexing quest ever since the discovery of the accelerating expansion of the universe. Building on a recent analysis of bubble-nucleation in the decay of (false-vacuum) AdS backgrounds where the interfacing bubbles [...] Read more.
Finding four-dimensional de Sitter spacetime solutions in string theory has been a vexing quest ever since the discovery of the accelerating expansion of the universe. Building on a recent analysis of bubble-nucleation in the decay of (false-vacuum) AdS backgrounds where the interfacing bubbles themselves exhibit a de Sitter geometry we show that this resonates strongly with a stringy cosmic brane construction that naturally provides for an exponential mass-hierarchy and the localization of both gravity and matter, in addition to an exponentially suppressed positive cosmological constant. Finally, we argue that these scenarios can be realized in terms of a generalization of a small resolution of a conifold singularity in the context of a (Lorentzian) Calabi–Yau 5-fold, where the isolated (Lorentzian) two complex dimensional Fano variety is a four-dimensional de Sitter spacetime. Full article
(This article belongs to the Special Issue Dark Energy and the Dark Sector in Supergravity, String Theory and Extra-Dimensions)
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