Special Issue "Gravitational Waves: Prospects after the First Direct Detections"

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

Deadline for manuscript submissions: closed (31 August 2020) | Viewed by 9489

Special Issue Editor

Institute of Physics, University of Szeged, 6720 Szeged, Dugonics tér 13, Hungary
Interests: cosmology and dark energy models; galaxy structure and dark matter models; gravitational lensing; Black holes, accretion and jets; gravitational waves from compact binaries supermassive black hole binaries: gravitational waves and jets; brane-worlds and black strings; general relativity; constrained dynamical systems; LIGO Scientific Collaboration

Special Issue Information

Dear Colleagues,

Tiny ripples of space-time curvature propagating with the speed of light were first detected by Advanced LIGO in 2015, one century after General Relativity, the theory correctly predicting gravitational waves, was formulated. These observational results certainly stand among the most important ones in contemporary physics, confirming General Relativity (or theories having the correct general relativistic limit) in a spectacular manner. The general excitement following the detections leaded to planning of new gravitational wave observatories while existing projects are sped up. On the theoretical side, the investigations concerning the properties of gravitational waves beyond the weak field regime and beyond General Relativity gained increased momentum.

The first detected gravitational waves squeezed the distances in the detectors by a mere one thousandth of the size of the proton, as they were emitted 1.3 billion years ago and 410 Mpc away. Being so weak at arrival, gravitational waves are well described by a linear approach, as perturbations of the flat space-time. Their sources, pairs of black holes of only a few solar masses are among the smallest ones in the universe, which harbors much bigger black holes in galactic centers. There is important gravitational wave physics well beyond the weak-field regime.

We invite colleagues to submit contributions to the Special Issue, "Gravitational Waves: Prospects after the First Direct Detections", of the journal Universe, addressing both theoretical and observational aspects concerning the

  1. first direct detections of gravitational waves,
  2. future gravitational wave experiments,
  3. strong-field gravitational waves in the geometrical optics approximation,
  4. backreaction of gravitational waves,
  5. gravitational waves as exact solutions of the Einstein equations,
  6. gravitational waves in modified gravity theories,
  7. observational and theoretical constraints on the speed and polarizations of gravitational waves,
  8. astrophysics and cosmology with gravitational waves,
  9. electromagnetic and high-energy cosmic ray counterparts of gravitational waves.

The contributions can be either shorter research papers or longer reviews. Publication, upon favorable review, is free of charge. The Special Issue will be also published as a book with ISBN number, provided it will contain at least 10 contributions.

Prof. László Árpád Gergely
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. 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.

Published Papers (3 papers)

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Research

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Article
Primordial Gravitational Waves and Reheating in a New Class of Plateau-Like Inflationary Potentials
Universe 2018, 4(7), 77; https://doi.org/10.3390/universe4070077 - 02 Jul 2018
Cited by 1 | Viewed by 2637
Abstract
We study a new class of inflation model parametrized by the Hubble radius, such that aHexp(αφ)n. These potentials are plateau-like, and reduce to the power-law potentials in the simplest case n=2 [...] Read more.
We study a new class of inflation model parametrized by the Hubble radius, such that aHexp(αφ)n. These potentials are plateau-like, and reduce to the power-law potentials in the simplest case n=2. We investigate the range of model parameters that is consistent with current observational constraints on the scalar spectral index and the tensor-to-scalar ratio. The amplitude of primordial gravitational waves in these models is shown to be accessible by future laser interferometers such as DECIGO. We also demonstrate how these observables are affected by the temperature and equation of state during reheating. We find that a large subset of this model can support instantaneous reheating, as well as very low reheating temperatures of order a few MeV, giving rise to interesting consequences for dark-matter production. Full article
(This article belongs to the Special Issue Gravitational Waves: Prospects after the First Direct Detections)
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Article
Gravitational Waves in Locally Rotationally Symmetric (LRS) Class II Cosmologies
Universe 2017, 3(4), 69; https://doi.org/10.3390/universe3040069 - 02 Oct 2017
Cited by 11 | Viewed by 2444
Abstract
In this work we consider perturbations of homogeneous and hypersurface orthogonal cosmological backgrounds with local rotational symmetry (LRS), using a method based on the 1 + 1 + 2 covariant split of spacetime. The backgrounds, of LRS class II, are characterised by that [...] Read more.
In this work we consider perturbations of homogeneous and hypersurface orthogonal cosmological backgrounds with local rotational symmetry (LRS), using a method based on the 1 + 1 + 2 covariant split of spacetime. The backgrounds, of LRS class II, are characterised by that the vorticity, the twist of the 2-sheets, and the magnetic part of the Weyl tensor all vanish. They include the flat Friedmann universe as a special case. The matter contents of the perturbed spacetimes are given by vorticity-free perfect fluids, but otherwise the perturbations are arbitrary and describe gravitational, shear, and density waves. All the perturbation variables can be given in terms of the time evolution of a set of six harmonic coefficients. This set decouples into one set of four coefficients with the density perturbations acting as source terms, and another set of two coefficients describing damped source-free gravitational waves with odd parity. We also consider the flat Friedmann universe, which has been considered by several others using the 1 + 3 covariant split, as a check of the isotropic limit. In agreement with earlier results we find a second-order wavelike equation for the magnetic part of the Weyl tensor which decouples from the density gradient for the flat Friedmann universes. Assuming vanishing vector perturbations, including the density gradient, we find a similar equation for the electric part of the Weyl tensor, which was previously unnoticed. Full article
(This article belongs to the Special Issue Gravitational Waves: Prospects after the First Direct Detections)

Review

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Review
A Review of Gravitational Waves from Cosmic Domain Walls
Universe 2017, 3(2), 40; https://doi.org/10.3390/universe3020040 - 05 May 2017
Cited by 66 | Viewed by 3984
Abstract
In this contribution, we discuss the cosmological scenario where unstable domain walls are formed in the early universe and their late-time annihilation produces a significant amount of gravitational waves. After describing cosmological constraints on long-lived domain walls, we estimate the typical amplitude and [...] Read more.
In this contribution, we discuss the cosmological scenario where unstable domain walls are formed in the early universe and their late-time annihilation produces a significant amount of gravitational waves. After describing cosmological constraints on long-lived domain walls, we estimate the typical amplitude and frequency of gravitational waves observed today. We also review possible extensions of the standard model of particle physics that predict the formation of unstable domain walls and can be probed by observation of relic gravitational waves. It is shown that recent results of pulser timing arrays and direct detection experiments partially exclude the relevant parameter space, and that a much wider parameter space can be covered by the next generation of gravitational wave observatories. Full article
(This article belongs to the Special Issue Gravitational Waves: Prospects after the First Direct Detections)
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