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Astronomy, Volume 1, Issue 1 (June 2022) – 6 articles

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Communication
Surface Electromagnetic Waves near a Black Hole Event Horizon and Their Observational Consequences
Astronomy 2022, 1(1), 49-57; https://doi.org/10.3390/astronomy1010006 - 07 Jun 2022
Viewed by 374
Abstract
Localization phenomena in light, scattering from random fluctuations of matter fields and space–time metrics near a black hole horizon, were predicted to produce a pronounced peak in the angular distribution of second-harmonic light in the direction normal to the horizon. Therefore, the detection [...] Read more.
Localization phenomena in light, scattering from random fluctuations of matter fields and space–time metrics near a black hole horizon, were predicted to produce a pronounced peak in the angular distribution of second-harmonic light in the direction normal to the horizon. Therefore, the detection of second-harmonic generation may become a viable observational tool to study spacetime physics near event horizons of astronomical black holes. The light localization phenomena near the horizon may be facilitated by the existence of surface electromagnetic wave solutions. In this communication, we study such surface electromagnetic wave solutions near the horizon of a Schwarzschild metric, describing a black hole in vacuum. We demonstrate that such surface wave solutions must appear when quantum gravity effects are taken into account. Potential observational evidence of this effect is also discussed. Full article
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Article
Exotic Cores with and without Dark-Matter Admixtures in Compact Stars
Astronomy 2022, 1(1), 36-48; https://doi.org/10.3390/astronomy1010005 - 29 May 2022
Cited by 1 | Viewed by 425
Abstract
We parameterize the core of compact spherical star configurations by a mass (mx) and a radius (rx) and study the resulting admissible areas in the total-mass–total-radius plane. The employed fiducial equation-of-state models of the corona at radii [...] Read more.
We parameterize the core of compact spherical star configurations by a mass (mx) and a radius (rx) and study the resulting admissible areas in the total-mass–total-radius plane. The employed fiducial equation-of-state models of the corona at radii r>rx and pressures ppx with p(r=rx)=px are that of constant sound velocity and a proxy of DYΔ DD-ME2 provided by Buchdahl’s exactly solvable ansatz. The core (r<rx) may contain any type of material, e.g., Standard-Model matter with unspecified equation of state or/and an unspecified Dark-Matter admixture. Employing a toy model for the cool equation of state with first-order phase transition, we also discuss the mass-radius relation of compact stars with an admixture of Dark Matter in a Mirror-World scenario. Full article
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Review
The Conformal Cosmological Potential
Astronomy 2022, 1(1), 17-35; https://doi.org/10.3390/astronomy1010004 - 02 Apr 2022
Viewed by 373
Abstract
We discuss qualitative features of the conformal relation between certain classes of gravity theories and general relativity, common to different themes such as f(R), Brans-Dicke-type, and string theories. We focus primarily on the frame relations of the fields involved, [...] Read more.
We discuss qualitative features of the conformal relation between certain classes of gravity theories and general relativity, common to different themes such as f(R), Brans-Dicke-type, and string theories. We focus primarily on the frame relations of the fields involved, slice energy, traceless and Palatini extensions, and selected cosmological applications. Full article
Editorial
Astronomy—Editorial
Astronomy 2022, 1(1), 15-16; https://doi.org/10.3390/astronomy1010003 - 18 Mar 2022
Viewed by 466
Abstract
Astronomy has a long history over thousands of years, since the creation of ancient civilization [...] Full article
Article
2+1 Einstein–Klein–Gordon Black Holes by Gravitational Decoupling
Astronomy 2022, 1(1), 2-14; https://doi.org/10.3390/astronomy1010002 - 24 Feb 2022
Cited by 3 | Viewed by 770
Abstract
In this work we study the 2+1-Einstein–Klein–Gordon system in the framework of Gravitational Decoupling. We associate the generic matter decoupling sector with a real scalar field so we can obtain a constraint which allows us to close the system of [...] Read more.
In this work we study the 2+1-Einstein–Klein–Gordon system in the framework of Gravitational Decoupling. We associate the generic matter decoupling sector with a real scalar field so we can obtain a constraint which allows us to close the system of differential equations. The constraint corresponds to a differential equation involving the decoupling functions and the metric of the seed sector and will be independent of the scalar field itself. We show that when the equation admits analytical solutions, the scalar field and the self-interacting potential can be obtained straightforwardly. We found that, in the cases under consideration, it is possible to express the potential as an explicit function of the scalar field only for certain particular cases corresponding to limiting values of the parameters involved. Full article
Editorial
Publisher’s Note: Have You Ever Looked at the Stars?
Astronomy 2022, 1(1), 1; https://doi.org/10.3390/astronomy1010001 - 27 Jul 2021
Cited by 1 | Viewed by 1405
Abstract
Have you ever looked at the stars [...] Full article
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